Peel, core and grate the apples. Stir in cinnamon, sugar, vanilla sugar and lemon zest. Set aside.
Position the rack in the center of the oven and preheat to 200°C (392ºF).
Mix all the cake layer dry ingredients in a medium size mixing bowl. Set aside about 1 cup of prepared mixture.
Divide remaining dry ingredient mixture. Spread evenly 1/2 of the mixture on the bottom of 320 mm x 228 mm x 50 mm (13″x 9″ x 2″) baking pan.
Divide grated apple mixture. Spread evenly 1/2 of the apple mixture in the baking pan, topping the dry ingredient layer.
Spread evenly second layer of dry ingredient mixture.
Top it up with second layer of apple mixture.
Sprinkle the top with the dry ingredient mixture preserved in the cup. Set aside for 15 minutes.
Bake for 40 minutes. Dust with confectioner’s sugar, cover the baking pan with kitchen towel (very important!!) and let cool completely, the best if left overnight.
Cut the cake into 50 mm x 38 mm (2″ x 1 1/2″) pieces and serve dusted with confectioner’s sugar.