Mix flour, baking powder, egg, lemon peel, sugar, vanillin sugar, salt and cold fat in flakes with the dough hooks of the hand mixer. With cool hands quickly work into a smooth dough.
Cover and put in a cool place for about 30 minutes. In the meantime, drain the apricots on a sieve. Drain the quark well as well. Separate the eggs. Mix egg yolk, quark, salt, milk and 100 g sugar.
Fold in pudding powder, lemon peel and lemon juice. Beat the egg white until stiff and gradually add the remaining sugar. Fold into the quark mixture. Grease a springform pan (26 cm Ø) and sprinkle lightly with breadcrumbs.
Roll out the dough between 2 layers of cling film to a circle (approx. 30 cm Ø). Line the mould with this, press the rim firmly and straighten with a dough wheel or knife. Prick the dough base several times with a fork.
Place the apricots on the dough with the rounding upwards and fill the quark mixture over them. Bake in the preheated oven (electric: 175 °C/ gas: level 2) for about 1 1/2 hours. Let the cake cool down on a cake rack.
Dust with icing sugar. Results in about 12 pieces.