Preheat the Oven: Preheat the oven to 180 degrees Celsius (top/bottom heat; for circulating air, set it to 160 degrees). Line a springform pan (⌀ 20 cm) with baking paper.
Prepare the Dough: In a metal bowl, whisk the eggs and sugar together over a water bath until the sugar dissolves.
Whip the Mixture: After that, whip it with a hand mixer or kitchen machine on the highest level for about 10 minutes until you achieve a stable egg foam. Mix in the lemon zest.
Sift and Fold: Sift the flour, cornstarch, and baking powder over the egg mixture and gently fold it in.
Add Butter: Melt the butter in a small saucepan, then fold it into the dough carefully.
Bake: Fill the dough into the prepared mold and bake in the preheated oven for approximately 20 minutes. Allow the cake to cool completely.
Prepare the Cream: Soak the gelatin leaves in cold water. In a saucepan, heat the milk and add the sugar, egg yolks, and vanilla pudding blend. Cook until it thickens, then remove from heat and add the gelatin.
Make the Whipped Cream: Allow it to cool slightly, then fold in the whipped cream.
Assemble the Cake: Once the sponge has cooled, cut it into three layers. Spread a layer of raspberry jam on the bottom layer, add a part of the cream, place the second layer on top, and repeat.
Final Touch: Cover the whole cake with the remaining cream and then drape the marzipan blanket over the cake, smoothing it out. Decorate with marzipan roses.