Grate the marzipan coarsely and whisk it together with butter, sugar, and vanilla sugar.
Whisk in the eggs.
Stir in the flour and salt.
Cut the apples into small cubes and fold them into the batter.
Spread the batter into an ovenproof dish (about 20x20 cm) lined with parchment paper.
Chop the almonds and mix together the sugar and cinnamon. Sprinkle the almonds and cinnamon sugar on top of the batter.
Bake for 30 minutes in a preheated oven at 175 degrees Celsius (347 degrees Fahrenheit).
Eat as is or serve with vanilla ice cream and powdered sugar.
The cake keeps well for a few days in the refrigerator.