Mix soft butter, sugar, cinnamon and egg yolk until very creamy,
then fold in the flour mixed with baking powder and the nuts,
Beat the egg whites into firm snow and stir in gently.
Pour 2/3 of the dough into prepared muffin molds (smooth with the back of a wet spoon), spread 1 teaspoon of jam and pour the rest of the dough over it - it works best if you sprinkle the dough on top.
Bake in the preheated oven at 150 ° for about 20 minutes.