Clean and wash the rhubarb and cut it into pieces about 1.5 cm wide. For the crumbles, roughly grate marzipan. Put 100 g fat in flakes, 75 g sugar and 150 g flour in a bowl. Knead into crumbles with the dough hooks of the hand mixer. For the sponge mixture mix 250 g fat and 200 g sugar with the whisks of the hand mixer until creamy. Stir in the eggs one after the other. Mix 300 g flour, starch and baking powder, stir briefly into the dough.
Put the dough into a greased fat pan of the oven and smooth it down. Spread the rhubarb on top and sprinkle with crumbles. Bake in the preheated oven (electric range: 175 °C/ convection oven: 150 °C/ gas: level 2) for 40-45 minutes. Let it cool down. Cut cake into pieces, sprinkle with pink sugar and decorate with lemon balm. Whipped cream tastes good with it