Melt 200 g butter, let it cool down a little. Put flour, 150 g sugar and salt in a bowl. Add 1 egg and liquid butter and knead into crumbles using the dough hooks of the hand mixer. Grease a springform pan (26 cm Ø). Add 2/3 of the dough and press it to a flat bottom. Put the mould and the crumbles in a cool place.
Cream 125 g butter, 100 g sugar and 1 packet vanilla sugar with the whisks of the hand mixer. Separate 2 eggs. Stir 2 egg yolks and 3 eggs individually into the butter mixture. Stir in quark, 1 packet of vanilla sugar and semolina. Beat 2 egg whites until stiff, while pouring in 50 g sugar. Spread the plum puree on the pastry base. Fold the beaten egg whites into the quark mixture and fill into the springform pan. Spread crumbles on top and bake in the preheated oven (electric range: 175 °C/ convection oven: 150 °C/ gas: level 2) for 50-60 minutes. If the surface gets too dark, cover with aluminium foil. Remove the cake from the oven and let it cool down on a cake rack. After about 15 minutes, remove the rim from the tin.
Spread the plum puree on the pastry base. Fold the beaten egg whites into the quark mixture and fill into the springform pan. Spread crumbles on top and bake in the preheated oven (electric range: 175 °C/ convection oven: 150 °C/ gas: level 2) for 50-60 minutes. If the surface gets too dark, cover with aluminium foil. Remove the cake from the oven and let it cool down on a cake rack. After about 15 minutes, remove the rim from the tin. Dust the cake with icing sugar before serving. Whipped cream tastes good with it