Put flour, 30 g sugar, salt and yeast in a mixing bowl and mix. Melt the fat. Add milk and warm up lukewarm. Put 1 egg, milk and fat into the mixing bowl and knead everything with the dough hooks of the hand mixer to a smooth dough. dust the dough lightly with flour and let it rise covered in a warm place for about 1 hour
Clean and wash the rhubarb and cut it into pieces about 1 cm wide. Wash lemon hot, rub dry. Finely grate the peel. Separate 2 eggs. Beat the egg whites with the whisks of the hand mixer until stiff. Mix quark, 150 g sugar, lemon rind, 2 egg yolks and pudding powder until smooth. Carefully fold in the rhubarb first, then the beaten egg white
Knead the dough on a floured work surface and roll out round (approx. 30 cm Ø). Line the bottom of a springform pan (26 cm Ø) with baking paper. Grease the rim. Put the dough into the tin, pressing the rim. Spread the quark mixture on top of the dough and smooth it down. Bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 50 minutes. Let the cake cool down in the switched off oven for about 3 hours. Leave the oven door ajar. Remove the cake from the tin and sprinkle with icing sugar
waiting time approx. 3 3/4 hours