For the dough, mix margarine with the sugar with a hand mixer at high speed for 2 minutes, then add the eggs, beating in each individually. Stir in the ground almonds, flour and cinnamon. Press dough with wet hands into a (20 x 30 cm/approximately 8 x 12 inches) baking sheet lined with parchment paper, forming an edge about a finger width high.
For the filling, peel the apples and cut in half. Remove the cores and cut the flesh into slices. Arrange the apple slices over the cake. Whisk eggs with the milk and pour over the apples. Sprinkle with vanilla sugar and bake on the second shelf from the bottom in a preheated oven at 225°C (approximately 425°F), about 25 minutes. Remove from baking sheet. When the cake has cooled to lukewarm, cut and serve.