Place in a bowl 200 grams of soft butter and zest of one lemon. Beat until white, add 2 teaspoons of vanilla sugar and, without stopping whipping, add 200 grams of granulated sugar. Add one by 4 eggs and continue to beat until a homogeneous lush mass is obtained. Add 275 grams of sifted white flour, change the mixer nozzle and knead the dough.