Combine the egg, sugar and butter and stir until creamy. Add the remaining ingredients, except for the plum jam, and knead a dough. The dough should now rest in the refrigerator for about half an hour.
Then put about 2/3 of the dough in a greased springer tin and press firmly. Now distribute the plum jam on top. Either cut out patterns with the remaining dough and distribute them on the cake or draw lines (grid) over them with a dough syringe. Then bake at 180 degrees for approx. 45 - 50 minutes (with convection 160 degrees - 50 minutes).
It is best to let the cake steep for 4-5 days before serving, because it tastes best. Of course, it`s also a real treat when it`s fresh.