Mix the butter, sugar, vanilla sugar, cinnamon, egg and egg yolk until frothy. Mix in flour and starch and fold in. Fill the dough into greased tartlet molds. Wash and drain the plums, cut the pitted fruit into wedges and press them into the dough in a circle. Bake in a preheated oven at 170-190 degrees for 15-20 minutes. Warm the orange jam gently while stirring. Remove the tart from the mold and cover with jam.