Key Lime Pie Cake

The Great Bakes of America continues and we’re using a classic American pie once again. To mix things up a little, we’re also adding spome zesty passion fruit – lime and passionfruit are a wonderful combination, complimenting once anopther brilliantly. And I love passion fruit. With a…erm, well with a passion.

key lime pie cake 5

I used Italian Meringue on this cake purely because of it’s stability – when making meringue, it’s the only way to do it in my opinion. Apart from, of course, the Swiss Meringue buttercream. Oh how I love thee so. So smooth, so creamy and so light! American buttercream is great an’ all, but it can sometimes overwhelm a cake with it’s sweetness. For this cake, I wanted it to be fresh tasting and for those sharp fruit flavours to power through.


Serves: 15

280g plain flour, sifted
170g butter, unsalted and softened
100g soft brown sugar
200g golden caster sugar
300ml buttermilk
3 eggs
3 tsp baking powder
salt, pinch
zest of 2 limes

3 passion fruit

4 egg whites
350g sugar
300g butter, cubed, unsalted and softened
2 tbsp lime juice
green food colouring

2 eggs whites
120g sugar
30ml water
pinch of cream of tartar

key lime pie cake 4

Preheat the oven to 170c fan and line two 6” cake tins.

For the cake, beat the butter, lime zest and sugar together until pale and fluffy. Add the eggs, one by one and mixing inbetween each addition to ensure the mixture doesn’t curdle. No worries if it does, just add a little flour to bring it back together.

Sieve the flour, salt and baking powder into a bowl and add a third of it to the batter before mixing for a few seconds and then adding half the buttermilk. Repeat the process and then add the final third of the flour. Scrape the bowl down and beat everything together to incorporate it. Split evenly into the cake tins and bake for 35-40 minutes on the middle shelf. Once baked, leave the cakes to cool before leveling off and cutting halfways so you’re left with four even layers.

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Put the eggs and sugar into a heatproof bowl over a pan of simmering water. Continuously mix until all the sugar dissolves – approximately 10 minutes. To test, take some of the mixture and rub it between your fingers. If you don’t feel any sugar granules, you’re done!

Off the heat, whisk with a balloon whisk on high until the mixture is completely cool and you get stiff peaks – again about 10 minutes. Add in, a cube at a time, the butter while the mixer is still whisking. Continue until all the butter is incorporated. Add the lime zest and the green food colouring. I used a gel and needed the tiniest bit as I didn’t want it to be bright green. But go for whatever you’re feeling! Once that’s mixed together nicely, it’s ready to use.

key lime pie cake 1

Place the first cake layer on a board or turntable and spread some of the buttercream on top. Level off and scoop out the pulp from one passionfruit – seeds and all! Repeat the process until all layers are done – the final layer should be the bottom half of one of the cakes, flipped upside down you’re left with a nice flat top. Give it a crumb coat to trap in any crumbs and put in the fridge for about an hour. Swiss meringue buttercream is wonderfully light, so needs a little bit more time to ‘stiffen up’ to ensure the cake is nice and secure.

Once cooled, do the final coat – generously spoon on the buttercream and level the top and sides with a pallet knife, finishing off with a cake leveler.

Mix 30ml of water with the sugar and heat to approx. 115°C – the sugar should be dissolved and it should start forming a syrup. Start beating the 2 eggs whites until foamy and then pour the syrup – a slow and steady stream – into the egg whites. You need to go slow as otherwise it’ll cook the egg whites and that’s never good!

key lime pie cake 2

Once you’ve reached still peaks, decant into a piping bag white with a large plain nozzle (I didn’t fit my piping bag with any nozzle to create these, but it depends on your piping bag) and pipe peaks on top of the cake. Finish off with a blow torch and serve!

key lime pie cake 3