1/2 cup butter, slightly softened (1 stick)
2/3 cup granulated sugar, plus more for garnishing
1 large egg
finely grated peel (yellow part only) of 1 large
lemon
1 3/4 cup all-purpose or unbleached white flour
1 large egg yolk beaten with 1 tablespoon water
For glazing cookies.

Grease 2 baking sheets and set aside. With a mixer at medium speed, beat the butter in a large mixer bowl until light and fluffy. Beat in the sugar until well blended and smooth. Beat in the egg and lemon peel. With the mixer at low speed, beat in the flour just until evenly incorporated.

Divide the dough in half. Place each portion between large sheets of wax or parchment paper. Rolling out the dough to a scant 1/4 inch thick.

Stack the rolled sheets of dough on a baking sheet. Refrigerate for 20 minutes or until cold and firm, but not hard.

Preheat oven to 375°F. Working with one chilled portion of dough at a time (keep the other one chilled), peel away a layer of paper.

Working with a few cookies at a time, brush the tops with the egg yolk-water mixture using a pastry or silicone brush.

Sprinkle the tops of the cookies lightly with granulated sugar.

Bake for 6 to 9 minutes or until the top is just tinged with brown and slightly darker at the edges.

Cool on baking sheets for 2 minutes, then ransfer to wire racks to cool.

Store in airtight container for up to a week, or freeze for longer storage.

Makes 50 to 60 cookies.