Mix the butter with sugar, vanilla sugar, saffron and salt until frothy. Mix in the eggs, add the yogurt and stir in. Add flour and baking powder. Place the dough on a greased tray and spread the plums over it.
Bake in a preheated oven at 170 ° C for about 40 minutes.
Bring the 100 g sugar to the boil with the water and simmer for approx. 5 minutes. Brush the warm cake with the water-sugar mixture, then let it cool down.