Beat the butter, softened at room temperature, together with the sugar using a mixer. Add the egg yolk and lemon zest and beat for another minute. Add the flour, salt and baking powder and knead a soft dough. Cover the dough and place it in the fridge for 20 minutes. Tear off walnut-sized pieces of dough, roll them in your hand and flatten them. Make a hollow in the middle with your finger. Arrange the pieces on a tray lined with parchment paper and bake for 15-20 minutes in an oven preheated to 160 degrees. The bottom should brown while the top stays white. Once the biscuits have cooled, spoon lemon cream into the hollow you made with your finger. Enjoy your meal!
