For the plum spot, prepare a dampfl from yeast, milk and sugar.
Beat the butter, egg yolks, salt and grated lemon zest until fluffy, then add the flour and the dampfl and knead well with a food processor (dough hook).
Leave to rise in a warm place for one hour. While this is happening, wash the plums, cut them in half and remove the seeds.
Place the risen dough in a buttered pan and cover with the plums.
Let rise again, then sprinkle with sugar and cinnamon and bake the plum patch in the oven at 170 °C for about 30 minutes.