Melt the butter. Arrange the biscuits tightly next to each other, pour on the melted butter. Peel the apples and grate them. Mix them with 1/2 the sugar and cinnamon and stir well.
Separately, beat the eggs with the other 1/2 of the sugar to foam. Add the flour with baking powder and vanilla. Stir until you get a homogeneous mixture.
Lay out the apple mixture over the biscuits, then pour on the cake mixture evenly on top. Bake in a preheated 356°F (180 °C) oven. Once the cake cools, sprinkle it with powdered sugar.