Preheat oven to 175°C (350°F). Beat eggs and sugar until pale and fluffy. Gently fold in flour and baking powder. Pour into a round cake pan and bake for 25–30 minutes. Let cool completely, then slice into 3 even layers.

For custard, heat milk with vanilla. In a bowl, whisk egg yolks, sugar, and cornstarch. Slowly pour in the hot milk while whisking. Return to pan and cook on low until thickened. Chill completely.

Place the bottom sponge layer on a cake plate. Spread with raspberry jam, then custard. Add second sponge layer and spread with whipped cream. Place final sponge layer on top.

Shape whipped cream into a dome over the cake. Roll out green marzipan into a thin sheet and gently cover the cake. Trim edges and dust lightly with powdered sugar.

Decorate with a pink marzipan rose on top. Chill for 1–2 hours before serving.