Warm the milk slightly, dissolve the yeast in it. Put the flour, 60 g sugar, salt, egg yolks and fat in a bowl. Add the yeast milk and knead everything into a smooth dough. Cover and let rise in a warm place for about 30 minutes.
Core the plums and cut into wedges. Knead the yeast dough again and press it into a greased tart pan (26 cm). Spread the plums on top. Mix the eggs, sour cream and remaining sugar. Pour over the plums.
Bake in the preheated oven (top / bottom heat: 200 degrees, convection: 175 degrees, gas: level 3) for about 30 minutes. Dust with powdered sugar and cinnamon.