Wash the plums, cut in half and remove the core. Then preheat the oven to 180 ° C top / bottom heat.
Mix the butter, sugar and salt until frothy. Then gradually add the eggs to the batter. Mix the flour with the baking powder and stir into the batter. Now gradually add the yoghurt and milk to the dough. When everything is mixed, grease a baking sheet and dust it with flour and then spread the dough on top. Spread the breadcrumbs on the dough and place the plums on top.
Briefly mix the butter, sugar and flour together and pour over the cake as a crumble.
Now bake for at least 40 minutes on the middle rack in the hot oven.