Gather all the ingredients and let it come to room temperature.
Heat the oven to 170 degrees Celsius.
Prep you cake pan with butter and flour.
Peel the apples and cut them in small cubes.
Put the butter, sugar and vanilla sugar in a bowl and mix until smooth.
Add the egss one by one while mixing.
Add the flour and mix until the mixture is nice and fluffy.
When the mixture is fluffy add the apples and mix well using a spatula.
Pour everything in your prepped cake pan and cover with some aluminum foil. Bake the cake with the foil for 40 minutes. After 40 minutes, remove the foil and bake for another 20 minutes.
Cool the cake on a wire rack for 10 minutes, then loosen the edges by running a knife along the sides of the pan.
Turn the cake and let it cool for 60 minutes. Or let it cool for 15 minutes so it will still be a bit warm. (Remember this for the cold and rainy days for some instant comfort!)