Sift powdered sugar and separately flour and ground almonds. Mix the powdered sugar with the soft butter. Knead in the flour, ground almonds, salt and baking powder. Then mix with the egg and knead the dough consistently (not too long). Let it set in the refrigerator for at least 30 minutes. Then roll it out and use or top it as you wish.
If you want, you can cut out the bottom (for desserts).