For the crumble dough, mix flour with baking powder, add the remaining ingredients and prepare a crumbly mixture. Spread half of the crumble mixture evenly on a greased baking tray. For the curd mixture, mix together butter, sugar, vanilla sugar and lemon juice until fluffy. Add the curd and egg yolks and mix well. Prepare a creamy beaten egg white and fold into the curd mixture with the semolina. Add the curd mixture on the crumble base, then spread the remaining crumble dough on top. Spread the prepared fruit pieces on the cake and bake in the preheated oven at 180 °C for about 45 minutes.