This is Prue’s take on the retro English angel cake. The pretty decoration is super-easy: a cocktail stick and stripes of pink icing are all you need.
For the génoise, fold the foiled parchment to divide the cake tin into three even sections (each measuring 20 x 10cm) with the parchment side facing upwards, and grease with melted butter. Heat the oven to 190°C/170°C fan/375°F/Gas 5.
Tip the eggs and sugar into a bowl set over a pan of gently simmering water. Gently whisk until the sugar has dissolved and the mixture reaches 43°C/109°F on the sugar thermometer.
Weigh the mixture in the bowl of a stand mixer, then record the weight. Attach the bowl to the mixer and, using the whisk attachment, whisk the mixture until it is thick and mousse-like, and leaves a ribbon trail when you lift the whisk.
Meanwhile, divide the flour evenly between three small bowls. Do the same for the butter. Stir the vanilla into one bowl of butter. Stir the raspberry flavouring and a small drop of pink food colouring into the second bowl of butter, and the lemon zest and a small drop of yellow food colouring into the third.
Divide the whisked egg mixture into three bowls. Working with one bowl of egg mixture, flour and butter at a time, sift the flour over the egg mixture and gently fold in. Add the butter and fold – work quickly to prevent the mixture collapsing.
Repeat Step 5 with the remaining bowls of egg mixture, flour and butter to give three mixtures – vanilla, raspberry and lemon. Pour each into a section of the cake tin and bake for 12–15 minutes, until the tops spring back when pressed. Cool a little in the tin, then transfer to a wire rack to cool completely.
For the Italian meringue buttercream, melt the sugar in 3 tablespoons of water very gently in a pan over a low heat. Meanwhile, whisk the egg white in the clean bowl of a stand mixer fitted with a whisk, to soft peaks. Once the sugar has completely dissolved, increase the heat to a rapid boil until the syrup reaches 121°C/250°F on a sugar thermometer.
Remove the pan from the heat. With the whisk at full speed, slowly pour the hot syrup onto the egg whites in a thin stream. Continue whisking until the meringue is very thick and glossy and has cooled to room temperature.
Gradually add the butter, whisking after each addition until the buttercream is smooth and thick. Chill until firm.
To assemble, trim the sponges so they are identical in size and height. Spread half the buttercream over the vanilla sponge and top with the raspberry sponge. Spread the other half of the buttercream over the raspberry sponge and top with the lemon sponge (you might not need all the buttercream).
For the fondant icing, sift the icing sugar into a bowl and add 1½–2 tablespoons of water to mix to a stiff, dropping consistency. Spoon one quarter of the icing into a small bowl and colour it pink. Spoon the pink icing into the piping bag fitted with a writing nozzle.
Spread the white fondant icing over the top (not the sides) of the lemon sponge. Pipe fine lines of pink icing across the width of the cake, spacing them 1cm apart. Using a cocktail stick, gently drag the icing lines in opposite directions through the white fondant to feather. Cut the cake into six even slices and serve.