Separating eggs. Beat the egg whites until stiff, 175 g sugar in the process. Stir in the egg yolks one by one. Sift flour, starch and baking powder on top and fold in. Line the bottom of a springform pan (28 cm Ø) with baking paper. Add the sponge mixture and smooth it down. Bake in the preheated oven (electric cooker: 175 °C/ circulating air: 150 °C/ gas: see manufacturer) for about 30 minutes. Take out and let cool down.
Soak the gelatine. Cut the sponge in half horizontally. Mix quark, yoghurt, lemon juice and 25 g sugar. Squeeze out the gelatine, dissolve and stir in 3 tbsp. yoghurt mass. Stir everything into the remaining yoghurt. Cool until the mass begins to gel. Whip cream until stiff and fold in.
Place the cake ring around the lower cake base. Spread 3/4 of the cream on top. Place the 2nd cake base on top. Spread the rest of the cream on top. Chill for at least 5 hours.
Berries selected. Cut lemon first into slices, then into slices. Decorate cake with berries and lemon.