Beat the fat, 100 g sugar, lemon zest and salt until fluffy. Separate the eggs. Stir in egg yolk. Stir in quark, sour cream and semolina. Beat the egg whites until stiff and carefully fold into the mixture.
Drain the cherries on a sieve. Put half of the curd semolina mixture into a greased casserole dish (1 1/2 litre capacity). Layer 2/3 of the cherries. Pour the rest of the curd cheese semolina on top.
Spread the rest of the cherries on top. Bake in the preheated oven (electric: 175 °C/ gas: level 2) for about 50 minutes. In the meantime prepare the chocolate sauce. Stir the sauce powder, remaining sugar and 3 tablespoons of milk until smooth.
Boil up the rest of the milk. Stir in sauce powder and bring to the boil again. Serve the sauce with the casserole.