Put the flour, baking powder and sugar in a bowl. Put the butter in flakes on top and mix. Add the zest of one lemon, egg, limoncello and the juice of half a lemon and work everything into a smooth dough. Wrap the dough in foil and place in the fridge for 30 minutes.
Shape the dough into balls the size of a walnut. Put some sugar on a plate and roll the dough balls in it and then place on a baking sheet lined with baking paper (keep a little distance).
Bake in the oven preheated to 170 ° C for about 10 minutes until the biscuits are golden brown.