Preheat oven to 180°C.
Peel and core the apples. Dice two of them and slice the rest of the apples. Put the diced and sliced apple into two different bowls and season them with a tablespoon of sugar, the juice and the grated peel of one lemon.
Whip the egg yolks with the sugar until creamy, then stir in the melted butter and gradually mix in the flour sifted with the baking powder. Stir in the diced apples.
Beat the egg whites until stiff peaks form and gently fold them into the batter.
If the batter is too thick, you can add a dash of warm milk.
Pour into a 24 cm greased and floured cake tin and arrange the sliced apples on the surface, in concentric circles.
Bake in preheated oven for 45 minutes, until it is golden brown on the surface.