1 1/2 sticks (6 ounces) unsalted butter, cut into pieces
1 large egg
2 teaspoons finely grated lemon zest (optional)
1 teaspoon pure vanilla extract
Colored sugars and silver dragées
In a small bowl, whisk the flour with the salt. Put the sugar in a food processor and process until very fine. Add the pieces of butter and process until the mixture is smooth and creamy. Add the egg, lemon zest and vanilla and process until smooth. Add the flour mixture and pulse just until a dough forms.
Transfer the dough to a sheet of plastic wrap and pat it into a disk 1 inch thick. Chill until firm, about 1 1/2 hours.
Preheat the oven to 350°. On a lightly floured surface, roll out the dough 1/8 inch thick. Stamp out shapes, cutting the cookies as close together as possible. Sprinkle the cookies with colored sugars or dragées. Transfer the cookies to nonstick or greased baking sheets, leaving 1 inch between them. Bake for 10 to 12 minutes, or until lightly browned around the edges. Transfer the cookies to racks and let cool.
The cookies can be stored in an airtight container between sheets of wax paper for 1 month.