Beat the butter until frothy. Stir in the sugar and vanilla sugar. Gradually add the five eggs and keep stirring. Mix the flour with the baking powder and add a tablespoon at a time. Pour the dough into a size 26 springform pan lined with parchment paper.
Core, peel and dice the apples and place on the batter.
Bake in the preheated oven at 175 ° C top / bottom heat for 65 minutes.
Brush with warmed apricot jam immediately after baking. To let it cool down.
Mix a viscous glaze from the powdered sugar and the rum. Use it to glaze the cooled cake.