1) Mix the two flours with sugar and a pinch of salt and place the mixture in a fountain on a work surface. Combine very soft butter in the middle
in flakes, the grated rind of the lemon and 3 egg yolks and work the ingredients until a homogeneous mixture is obtained. Form a dough, wrap it in the food film and let it rest for 30 minutes.

2) Take a nut of dough, form a ball and flatten it slightly. Repeat the passage until the dough is finished.

3) Arrange the balls on a baking sheet lined with baking paper, practice on each an incision in the center with the blade of a knife and then brush with the remaining yolk, diluted with a few drops of water. Bake cookies in the oven preheated to 180 degrees for about 25 minutes until they start to brown; let them cool on a wire rack.