Melt the margarine over a mild heat and let it cool down again. Meanwhile preheat the oven to 180 ° C.
Beat the yogurt, eggs, sugar, vanilla sugar, salt, cinnamon and rum with the hand mixer until frothy. Pour in margarine in a thin stream. Mix the semolina with the baking powder and stir in.
Grease a springform pan (26cm) and sprinkle with breadcrumbs. Pour in the batter and distribute the well-drained plums (cut side up) on top.
The cake for about 40-45min. to bake. Let cool and remove from the mold.
Tip: If you like, you can sprinkle it with powdered sugar or cinnamon sugar or spread plum jam as you like.