For the dough: Mix butter, sugar, egg yolks, flour, baking powder, milk, vanilla sugar (or the inside of the vanilla pod) to form a dough. Pour into a greased, oblong cake tin. Peel and core the pears and cut into small pieces. Press evenly into the dough.
Bake in a preheated oven at 180 ° C for 20 minutes.
For the topping: Beat eggs, vanilla sugar and sugar until frothy. Stir in the sour cream. Spread on top of the cake. Bake covered for another 25 minutes.