How to make
Mix the wheat flour with 2 tbsp of the corn flour.
Add the softened butter, powdered sugar, salt and vanilla. Grate the rinds of the lemons and add them to the mixture.
Knead a dough, form a tube and put it in the freezer for 1 hour. Take it out, smear it with the whipped egg white and sprinkle on the remaining corn flour.
Cut it into slices, arrange them in a tray covered with baking paper and bake 15 min. at 370°F (190 °C).