Wash the apple, rub dry and cut into slices. Sprinkle with lemon juice. Knead 100 g flour, 60 g butter, 30 g sugar and cocoa into crumbles with your hands. Keep cold. In the meantime, whisk 60 g butter, 50 g sugar, vanillin sugar and salt with the whisks of the hand mixer until creamy white. Add the eggs one by one and stir in.
Mix 140 g flour and baking powder and stir alternately with the milk into the fat egg mass. Pour the dough into a greased and floured tart mould (20 cm Ø) and smooth it down. Cover with apple slices. Spread the crumbles irregularly on top. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for 35-40 minutes. Take the cake out of the oven and let it cool down on a cake rack