Peel, quarter, core and cut apples into slices. Mix starch, 4 tablespoons sugar and 40 ml lemonade until smooth. Boil 250 ml lemonade. Stir in the mixed starch and bring to the boil again. Simmer for 2-3 minutes.
Add apple slices, remove pot from stove.
Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Grease a tart mould with a lifting base (26 cm Ø). Cream 100 g butter, 150 g sugar and 1 pinch of salt. Stir in eggs one after the other.
Mix flour and baking powder and stir into the butter-sugar cream with 4 tbsp. lemonade.
Smooth the dough in the tin and spread apple compote on top. Bake the cake in a hot oven on the lowest shelf for about 40 minutes.
Reduce oven temperature (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Cover the cake with baking paper if necessary. Continue baking for about 30 minutes. Remove and leave to rest in the pan for approx. 10 minutes.
Carefully lift out of the mould and let it cool down.