Mix the flour with the baking powder and place in a mixing bowl. Add the cold butter, sugar, pinch of salt and egg and make a kneading dough. Wrap the dough in foil and place in the refrigerator for about 30 minutes.
Mix the quark well with the eggs in a bowl. Stir in the sugar and vanilla sugar. Whip the cream with the cream until stiff and fold carefully into the curd mixture.
Line the bottom of the springform pan with baking paper and lightly grease the edge. Roll out the dough on the floor and pull up an approx. 3 - 4 cm high edge. Sprinkle the pastry base with semolina and distribute the white grapes on top. Pour the quark mixture onto the grapes and smooth it out.
Place the cake in the (fan-assisted) oven preheated to 180 degrees and bake for approx. 50 - 55 minutes. When the baking time is over, take it out of the oven, let it cool down for 15 minutes, remove the edge of the springform pan and let it cool down.
Halve the red grapes and remove the seeds if necessary. Now place the grapes with the cut on the cake. Cook the icing according to the instructions, let it cool down a little, spread it on the cake and let it set.