Name: Delia Smith Lemon and Blueberry Cake Recipe
Prep time: 45 min
Cook time: 30 min
Total time: 135 min
Ingredients: 135 g butter (softened, plus extra for greasing); 100 g full-fat Greek yoghurt; 3 medium eggs; 1 unwaxed lemon (zest and juice); 150 g self-raising flour; 135 g golden caster sugar; 150 g blueberries (fresh or frozen); 250 g unsalted butter (softened); 500 g icing sugar (sifted); 1 tsp vanilla extract; a little milk (to loosen); 3 tbsp blueberry jam; extra full-fat Greek yoghurt; extra blueberries; extra lemon zest

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This Delia Smith lemon and blueberry cake recipe makes a tall, soft sponge with Greek yoghurt, lemon zest and plenty of blueberries. It’s finished with a buttercream that’s streaked with blueberry jam. The cake is small, made in two 15cm (6 inch) tins, so it suits a birthday for a few people or an afternoon tea.

One thing to know before you start. The recipe sits on Delia Online, but the page credits it to Juliet Sear’s book Air Fryer Baking Magic. It’s written for an air fryer, and I couldn’t find an official oven version. So I’ve worked out an oven method below and I’ve said clearly where it’s my own reading and not the source’s.

Jump to the recipe card at the end of this page for exact quantities and a printable version.

What’s in It

The sponge uses softened butter, full-fat Greek yoghurt, medium eggs, the zest and juice of a lemon, self-raising flour, golden caster sugar and fresh blueberries. The buttercream is unsalted butter, icing sugar, vanilla extract and a splash of milk. Blueberry jam goes in the middle and gets swirled through the outside. You’ll need two 15cm (6 inch) round tins or silicone moulds, baking paper, an electric whisk and a palette knife. A toothed cake scraper gives the streaky finish. Check that your tins fit in your air fryer before you start, because that catches a lot of people out (more on that below).

Lemon and Blueberries

Use an unwaxed lemon and zest it before you squeeze it, because it’s much easier that way. Fresh blueberries are the first choice, but frozen ones work if you add them straight from the freezer. In my reading, thawed berries leak more juice into the batter, so I’d keep them frozen and give the cakes a few extra minutes.

How I Make It

Prepare the tins and heat. Grease two 15cm (6 inch) tins and line the bases with baking paper. Turn the air fryer on to 140°C so it’s hot when the cakes go in. If you’re using an oven instead, see the oven section further down.
Mix the batter in one bowl. Put everything for the sponge, except the blueberries, into a large bowl. Whisk with an electric whisk just until it comes together. Stop there, because extra beating makes a tighter, drier crumb. Room temperature butter and eggs mix more smoothly. If the batter looks a little split, the flour usually pulls it back together.
Layer the berries. Spoon half the batter into the tins, scatter over half the blueberries, then add the rest of the batter. Finish with the remaining berries on top. The batter is thick, and the middle layer of fruit helps keep the berries spread through the cake instead of dropping to the bottom.
Air fry at 140°C for 25 to 30 minutes. The cakes should be risen and golden, with the edges just starting to pull away from the tin. A skewer in the middle should come out clean. Push the skewer into the batter between berries, because a berry will smear and look wet even when the cake is done. If the tops brown too fast, lay a loose piece of foil over them. If both tins won’t fit, bake one at a time and put the second one in straight after the first comes out.
Leave the cakes in their tins for 10 to 15 minutes, then turn them out onto a wire rack. Let them cool completely before you ice them. My estimate is about an hour, and warm sponge will melt the buttercream. If the tops have domed, trim them level with a serrated knife.
Beat the buttercream. Beat the butter on its own until smooth and creamy. Add the sifted icing sugar a little at a time, then the vanilla. Loosen it with a little milk so it spreads easily, but stop while it still holds its shape. Adding the sugar gradually keeps the icing sugar out of the air and out of your hair.
Fill the cake. Put the first layer on your plate or stand and spread about 150g of buttercream over it. Make a shallow well in the middle with a palette knife and push the buttercream out to the edge. Spoon 2 tablespoons of jam into the well. The ring of buttercream holds the jam in. Set the second layer on top.
Cover and swirl. Spread the remaining buttercream over the top and sides. Dot the rest of the jam around the sides and over the top. Drag a toothed scraper around the sides to pull the jam through, then swirl the top with the tip of a palette knife or the handle of a teaspoon. Don’t keep going once you see streaks, or the whole cake turns purple. The texture hides small mistakes, so it doesn’t need to be neat.

The Delia Smith Link Nobody Explains

If you searched for Delia Smith’s lemon and blueberry cake, you might expect one of her classic sponges. This isn’t one. The page on Delia Online credits the recipe to Juliet Sear’s book Air Fryer Baking Magic. I confirmed from publisher listings that the book exists and came out in July 2024 from HarperCollins. I haven’t been able to open the book, so I’m relying on the Delia Online page for the fact that this exact cake is in it.

Juliet Sear has other blueberry and lemon cakes online, and they’re different. The ITV This Morning site has a bigger layer cake made in two 20cm tins with different amounts, baked in an oven at 170°C fan. Don’t mix its numbers with the ones here. Everything on this page is the air fryer cake for 15cm tins. I’m not connected to Delia Smith or Juliet Sear.

The Oven Times Nobody Mentions

The source gives one temperature, 140°C in an air fryer, and no oven figure. Some recipe sites online give a fan oven range of 160 to 170°C without saying where it comes from.

Here’s my reading. An air fryer pushes hot air around harder than a fan oven, so air fryer recipes use lower numbers. A common rule of thumb is to add about 20°C when you move to a fan oven. That gives 160°C fan, 180°C conventional, gas mark 4. I’d start checking at 25 minutes, and I’d allow up to 35. That’s a starting point and not a tested time, so go by the skewer and the golden colour. The good news is that most ovens take both tins at once, so you skip the batch baking.

How Many Slices You Really Get

Delia Online says this cake serves 8 to 10. Other copies of the recipe say 8 and give 580 calories a slice. I worked this out by adding up typical values for every ingredient, including all of the buttercream, and I get roughly 6,360 calories for the whole cake.

Cut Into	Calories Per Slice	Notes
8 slices	795 kcal	Generous wedges
10 slices	635 kcal	Top of the source’s range
12 slices	530 kcal	Small slices, fine for a tall rich cake

So the 580 figure looks too low to me. The buttercream alone (250g butter and 500g icing sugar) makes up about 60 percent of the total. These are estimates, because brands and egg sizes vary.

Tin Sizes and Scaling

A 15cm tin is small. Swapping to a bigger tin changes the depth of the cake and the bake time, so here’s the arithmetic. I worked out the area of each tin as pi times the radius squared, then compared it with the 15cm tin.

Tin Size	Area	Compared With 15cm	Air Fryer Fit
15cm (6 inch)	177 cm²	1×	Check yours
18cm (7 inch)	254 cm²	1.4×	Only large models
20cm (8 inch)	314 cm²	1.8×	Unlikely, check
23cm (9 inch)	415 cm²	2.3×	Very unlikely

For two 20cm tins, I’d double the sponge. That’s my arithmetic and I haven’t baked it. The 20cm tin has 1.8 times the area, so doubling the batter makes layers about 12 percent deeper than the 15cm cake (2 divided by 1.78). Expect a longer bake, and start checking at about 35 minutes in an oven. For the buttercream, the top is 1.8 times bigger but the sides only about 1.3 times bigger, so I’d go for 1.5 times the buttercream and jam, not double.

Ingredient	15cm (Source)	Two 20cm Tins (Calculated)
Butter (Sponge)	135 g	270 g
Greek Yoghurt	100 g	200 g
Medium Eggs	3	6
Lemons	1	2
Self-Raising Flour	150 g	300 g
Golden Caster Sugar	135 g	270 g
Blueberries	150 g	300 g
Butter (Buttercream)	250 g	375 g
Icing Sugar	500 g	750 g
Blueberry Jam	3 tbsp	4–5 tbsp

The column for the larger cake is for people who want a party size. If you want to stay close to the original, stick to the 15cm tins.

Common Mistakes and How I Fixed Them

Berries sank to the bottom. Cause: thin batter, skipping the layering, or wet berries. Fix: layer the batter and berries in two stages, and use berries straight from the freezer or patted dry.
The top browned before the middle set. Cause: the heating element in an air fryer sits close to the top of the tin. Fix: cover loosely with foil for the last part of the bake and start checking early.
The skewer looks wet. Cause: it went through a blueberry. Fix: test again in a spot with only batter.
The batter looks curdled. Cause: cold eggs meeting soft butter. Fix: use room temperature eggs. The flour usually brings it back together anyway.
The icing turned purple. Cause: too much dragging with the scraper. Fix: use fewer passes and stop when you see streaks.
The buttercream is sliding. Cause: the cake was still warm, or too much milk went in. Fix: cool the layers fully, add milk a teaspoon at a time, and chill the icing for 15 minutes if it’s soft.
Jam is leaking from the sides. Cause: no buttercream wall around it. Fix: spread the buttercream to the edge and keep the jam in the well.

Substitutions

Plain flour and baking powder. UK sources I found mostly say 2 level teaspoons of baking powder per 150g plain flour. One baker’s test came out at 1 teaspoon per 100g, which is closer to 1.5 teaspoons. Both are close. Sift them together well so the baking powder is spread evenly.

Another jam. Raspberry or blackcurrant jam works for the swirl. The flavour changes, but the look is similar.

Yoghurt. The recipe calls for full-fat Greek yoghurt. Lower-fat versions have more water and less fat, so the crumb may come out less rich. I’d stick to full-fat.

What to Serve With It

A spoonful of extra Greek yoghurt on the side balances the sweet buttercream. Fresh blueberries and a little extra lemon zest on the plate look good. A pot of tea or a strong coffee suits it well. Vanilla ice cream works too if you’re serving it as a pudding.

Make Ahead, Storing and Freezing

Make ahead. Bake the layers a day early, wrap them well and keep them at room temperature. Ice them on the day. The buttercream can be made ahead and kept covered in the fridge for a few days. Let it soften and beat it again before using.

Storing. Keep the iced cake in an airtight container somewhere cool for up to 3 days. In warm weather, keep it in the fridge so the buttercream doesn’t soften too much, and take it out about 30 minutes before serving.

Freezing. Wrap the un-iced layers in cling film and freeze for up to 1 month. Thaw them fully before icing. For slices of the finished cake, my approach is to freeze them on a tray first and then wrap them, so the icing doesn’t get squashed.

FAQs

Is this really Delia Smith’s recipe?

It’s hosted on Delia Online but credited to Juliet Sear’s book Air Fryer Baking Magic (HarperCollins, 2024).

Can I bake it in a normal oven?

I think so, but the source only gives an air fryer temperature. My conversion is 160°C fan, 180°C conventional or gas mark 4, and I’d start checking at 25 minutes. It’s untested, so go by the skewer.

Will two 15cm tins fit in my air fryer?

Smaller baskets may only take one. Check the tin fits with a gap all round so air can move, and bake one at a time if you need to. Put the second tin in as soon as the first comes out.

Can I use frozen blueberries?

Yes. Use them straight from the freezer and add a few minutes to the bake. Thawed berries leak more juice into the batter.

Why did my blueberries sink?

The batter may have been too thin, or you may have mixed all the berries through it. Layer the batter and berries in two stages as in the method, and keep the berries dry.

Can I use plain flour instead of self-raising?

Yes, with baking powder added. About 2 level teaspoons per 150g of plain flour is the figure most UK sources give. Sift them together.

How many slices does it make?

The source says 8 to 10. If you want smaller slices, you can get 12 from a tall 15cm cake, at about 530 calories each by my estimate.

Can I use low-fat yoghurt?

The recipe uses full-fat Greek yoghurt. Low-fat has more water and less fat, so the sponge may be less rich and moist. I’d use full-fat.

One Last Thing

This is a good small party cake, and the method is simple even if it looks fancy. Bake it once before an event so you know how your own air fryer or oven behaves, then adjust the time. If you want the original method and her other air fryer bakes, Juliet Sear’s book is the place to look.

Delia Smith Lemon and Blueberry Cake Recipe

Nancy Wilson