Grandmother's recipe for apple pie

Apple pie according to grandma's original recipe

300g butter (soft room temperature)
300g sugar
8 egg yolks
8 egg whites
300g wheat flour
1/2 packet baking powder
3 apples

Peel and core the apples and cut them into small long pieces.
Beat the butter until fluffy, add the sugar.
Add the egg yolks one at a time while stirring constantly.
Beat the egg whites until stiff and carefully mix into the butter-sugar mixture.
Finally, sift the flour with the baking powder into the mixture and stir in.
Bake at 180°C for 45 minutes.
Brush the cake with apricot jam while it is still hot for a nice shine.

Tips:
For a richer cake, you can replace 50g of the wheat flour, with whole grain flour.
You can also add in some chopped walnuts or hazelnuts with the flour.
A little cinnamon and / or vanilla sugar also adds flavour.
Instead of apples, you can also use pears or cherries.