Mix butter and sweetness until creamy. Stir in eggs, flour and baking powder. Spread into a greased springform pan (24 cm Ø). Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: level 2) for about 25 minutes. Let cool off
Soak the gelatine in cold water. Cut apples into slices. Steam with juice and 100 ml water for about 5 minutes. Flavour with cinnamon and sweetener. Take out about 10 slices. Squeeze the gelatine, dissolve in the hot apples, cool
Spread apples on the ground. Cool down. Stir the quark until smooth. Whip cream until stiff, fold in. Season to taste with sweetener. Spread on the apples. Decorate with the rest of the apples and cinnamon