Cream the butter and sugar together.
Add the egg and mix well.
Sift in cake flour and baking powder, and combine.
Shape the dough into balls and place them on a baking tray.
Gently press the center and fill with jam.
Bake in a preheated oven at 180°C (356°F) for 12-15 minutes.
Let the cookies cool, then plate them.