Hibiscus & yuzu layer cake

Preheat the oven to 180°C, gas mark 4. Grease 3 x 18cm round sandwich tins and line the bases with baking parchment. Use an electric hand mixer or a free-standing mixer to cream the butter, sugar and the zest of 1 lime for 4-5 minutes until light and fluffy. Beat in the eggs one at a time, beating well after each addition. Fold in the flour, almonds, salt and hibiscus until combined. Finally, fold in the milk 1 tbsp at a time until you get a batter that will drop off a spoon easily. Divide equally between the tins and level the tops with the back of a spoon. Bake for 22-25 minutes, swapping the tins around after 20 minutes if they are on 2 shelves, until golden, risen and just coming away at the edges. Remove from the oven, then leave to cool in the tins.

Meanwhile, make the curd. Put the yuzu juice in a small bowl and stir in the hibiscus; set aside for 20 minutes to infuse. Line a sieve with kitchen paper and strain the juice into a heatproof bowl, pressing well and carefully squeezing the last bits through with your hands; discard the hibiscus sediment. Add the lime juice, sugar, egg yolks, whole egg and a pinch of salt and use a balloon whisk to whisk until combined. Set the bowl over a pan of simmering water (ensuring the water doesn’t touch the base) and add the chilled, cubed butter. Whisk continuously over a gentle simmer for 10-15 minutes until the mixture thickens into a curd. Remove the bowl from the heat, then scrape the curd into a shallow bowl and cool a little at room temperature. Cover the surface of the curd with baking parchment; chill until needed.

For the buttercream, put the egg whites, icing sugar and a pinch of salt in a large heatproof bowl over the pan of simmering water (ensuring the water doesn’t touch the base). Use an electric hand mixer to whisk the mixture until thick and stiff (5-7 minutes). Take off the heat, spoon into a cold large bowl and keep whisking until the mixture is cool (about 5 minutes). Whisk in the butter, a little at a time, until incorporated and silky. Chill the buttercream for 30 minutes.

To assemble the cake, carefully remove the sponges from the tins. Put a small dollop of buttercream onto the centre of a cake board or cake plate and secure the bottom sponge in place (a cake turntable is useful if you have one). Use a palette knife to spread the sponge with 1⁄3 of the buttercream, then spread over 1⁄3 of the curd (loosen the curd with a few drops of water if it’s a bit stiff). Top with the second sponge, another 1⁄3 of buttercream and 1⁄3 of curd. Top with the final sponge and spread the top with 3⁄4 of the remaining buttercream. Use the remainder to thinly coat the sides, allowing the curd to catch in it, creating a ripple effect. Chill for 10 minutes.

Add a few drops of water to the remaining curd, then spoon it over the top of the cake, letting it drip down the sides in places. Scatter with the remaining lime zest and either serve immediately or chill until ready to eat, letting it sit at room temperature for a few minutes before slicing.