Drain the juice from the lemon, grate the rind and add them to the mixture. Add the butter that has been melted at room temperature. Sift the flour with the baking powder and knead a soft dough.
Leave the ready dough for about 30 min. in the fridge to harden.
Form small balls and put them in an oven dish laid out with baking paper.
Bake in preheated oven, taking care not to burn them.