Heat the milk and margarine until the margarine has melted. Stir in the yeast until it has dissolved.
Put all other dough ingredients in a mixing bowl. Add the milk-margarine-yeast mixture and knead everything into a yeast dough. Cover it and let it rise in a warm place.
In the meantime, wash and stone the plums.
When the dough has risen to about twice its size, roll it out thinly on a prepared baking sheet (fruit cake sheet) and cover with the plums. Now let everything rise again for about 10 minutes.
In the meantime, preheat the oven to 180 ° C fan oven or 200 ° C top / bottom heat.
Bake the cake on the middle rack for about 25 minutes.