Start the oven at 175 degrees Celsius.
Divide the plums in two and take away the core.
Use an electrical mixer to mix the icing sugar and egg yellows to a fluffy mixture.
Add the butter bit by bit while stirring.
Add the vanilla sugar, flour and baking powder to the mixture.
Add the butter bit by bit while stirring.
Add the vanilla sugar, flour and baking powder to the mixture.
Whip the egg whites to a firm foam.
Add the egg white foam gently in the mixture while slowly stirring with a spoon.
Add the mixture in the pie form.
Place the plums with the round side down evenly in the batter.
Place in the oven for 40 minutes.
Take out the cake and let cool down.
Before serving sprinkle some icing sugar on the cake.