Quarter and peel the apples, remove the core and cut into thin wedges. Squeeze the lemon. Mix the apple pieces with the lemon juice.
Melt the butter in a pan. Sprinkle with sugar and heat. Deglaze with calvados. Roughly chop the walnuts, add to the pan and caramelize lightly. Add apples, sultanas and cinnamon. Steam for five minutes. Take it from the stove and let it cool off.
Mix the butter, sugar, vanilla sugar and salt until creamy. Stir in eggs and almonds. Mix flour with baking powder and cocoa, sift over and stir in.
Put the batter into a greased, floured tart pan (approx. 26 cm diameter) and smooth it out. Spread the apples with the nuts and sultanas on top. Bake in the oven at 180 degrees for about 25 to 30 minutes. Take out of the oven.
Put the jam in a saucepan and heat while stirring. Spread on the still warm cake. Let cool and sprinkle thickly with powdered sugar.
P.S. I used my exotic Christmas jam for the recipe. Exotic Christmas jam You can of course use others. E.g. orange or peach jam.