Mix oil, milk, quark, 80 g sugar and 1 packet of vanilla sugar with the whisks of the hand mixer. Mix flour and baking powder and knead into the quark mixture with the dough hooks of the hand mixer.
Roll out the dough on a floured work surface to the size of the fat pan. Grease the fat pan and dust with flour. Put the dough into it and press the edge of the pan up a little. Peel apples, cut into eighths, removing the core.
Sprinkle eighths with lemon juice and place on the quark oil dough. Mix sour cream, eggs, 30 g sugar and 1 packet of vanillin sugar and pour over the apples. Chop the walnuts and sprinkle over the apples.
Bake in the preheated oven (electric oven: 175 °C/ gas: level 2) for approx. 40 minutes. Let the cake cool down and cut it into about 20 pieces.