Citrus Sugar Cookies
Line 2 baking sheets with parchment. Using an electric mixer, beat the butter, granulated sugar, and zest on medium-high until light and fluffy, 2 to 3 minutes. Beat in the egg, then the vanilla and salt.
Reduce mixer speed to low and gradually add the flour, mixing until just combined (do not overmix). Shape into a 1-inch-thick disk, wrap in plastic wrap, and refrigerate for at least 2 hours and up to 3 days.
Heat oven to 350° F. On a floured surface, roll the dough ¼ inch thick. Using lightly floured 2- to 3-inch cookie cutters, cut the dough into shapes, flouring the cutters and rerolling the scraps as necessary. Place the cookies 1 inch apart on the prepared baking sheets. Sprinkle with decorating sugar, if using.