Mix the soft fat, 300 g sugar, 750 g flour, baking powder and 2 eggs with the dough hooks of the hand mixer into crumbles. Spread 2/3 of the amount on a deep fat pan of the oven, coated with fat, and press it down.
Crumble the remaining dough and 2 tablespoons of flour with your hands and chill. Separate 6 eggs. Whisk 4 eggs and 6 egg yolks in a large mixing bowl with the whisk of the hand mixer for about 10 minutes until thick and creamy, adding 300 g sugar.
Mix the quark, mascarpone and half of the lemon peel. Stir in pudding powder. Stir in the egg-sugar mixture. Whip cream and egg whites separately until stiff. Fold the cream first, then the beaten egg white into the quark mixture.
Spread the curd mixture on the bottom of the fat pan. Spread with cooled crumbles. Bake in the preheated oven (electric: 175 °C/ gas: level 2) for 50-60 minutes. In the meantime, mix the remaining lemon and orange peel and 75 g sugar.
Spread on the cake pieces just before serving.