Step 1

Preheat oven to 160C. Beat butter and sugar in an electric mixer until creamy. Add eggs one at a time, then add vanilla seeds and lemon rind. Meanwhile, sieve flours and bicarbonate of soda into a bowl with a pinch of salt. With mixer on low speed, add half the flour mixture, then half the buttermilk. Repeat, then spoon mixture into a buttered 22cm x 32cm cake tin lined with baking paper. Smooth top, then bake until cake is golden and an inserted skewer withdraws clean (35-45 minutes). Cool in tin for 10 minutes, then invert onto a rack and cool completely.

Step 2

For vanilla frosting, combine eggwhite and cream of tartar in an electric mixer and whisk until frothy. Meanwhile, bring 240gm caster sugar and 120ml water to the boil in a saucepan over medium heat, stirring to dissolve sugar, then gradually add remaining sugar to eggwhite and whisk on medium speed until soft glossy peaks form. Continue cooking syrup to soft ball stage (115C; 4-8 minutes). Remove from heat, then gradually add hot syrup to whites, whisking continuously on medium-high speed. Add vanilla seeds and whisk until cool and glossy (10-20 minutes). Gradually add butter a little at a time, whisking continuously until incorporated and smooth (see note).

Step 3

Spread frosting over cake, scatter with raspberries and serve.