Knead the egg yolks, butter, sugar, flour, baking powder, salt and zest from one lemon into a smooth dough. Let the dough rest in the refrigerator for about 1 hour and then line a greased tart pan with the dough. Bake in a preheated oven at 180 ° C top / bottom heat for 20 minutes.
Meanwhile, mix the condensed milk with the juice of the two lemons and the zest of one lemon and pour on the slightly cooled base. Beat the two egg whites with 1 tablespoon of sugar until stiff and spread the egg whites over the filling. Bake for another 20 minutes at 180 ° C.