Add flour, salt, cocoa powder, 40 g sugar, 1 egg and butter in flakes and knead to a smooth shortcrust pastry. Chill for 30 minutes. Grease a springform pan (24 cm Ø) and dust with flour. Roll out the dough on a well floured work surface (30 cm Ø) and line the springform pan with it. Wash and quarter the apples, remove the core. Cut apple quarters into thin slices. Put slices in a bowl with water and lemon juice.
Mix pudding powder, cream, sour cream, 50 g sugar and 2 eggs. Spread apple slices on the dough in a circle. Pour the pudding evenly on top. Sprinkle with flaked almonds and 2 tablespoons of sugar. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for about 45 minutes. Remove and place on a cake rack. Remove the cake from the edge of the springform pan with a knife and let it cool down