Freshly grated lemon zest brightens up these buttery cookies.
In the bowl of a standing electric mixer fitted with a paddle, beat the butter until creamy. Add the 1 cup of turbinado sugar and the lemon zest and beat at medium speed until fluffy. Add the egg yolk and beat until smooth. In a medium bowl, whisk the flour with the salt and baking powder. Beat the dry ingredients into the butter at medium-low speed; the dough will be very soft.
Divide the dough in half and place each half between 2 large sheets of parchment paper or plastic wrap. Roll out the dough 1/4 inch thick and transfer to 2 baking sheets. Refrigerate until firm, at least 30 minutes.
Preheat the oven to 375°. Working with one piece of dough at a time, remove the top sheet of parchment and invert the dough onto a lightly floured surface; remove the second sheet of parchment. Using a floured 3-inch cookie cutter, stamp out cookies as close together as possible. Transfer the cookies to parchment paper–lined baking sheets and sprinkle with turbinado sugar. Bake for 12 to 14 minutes, or until golden. Let cool on the baking sheet for 10 minutes, then, using a metal spatula, transfer to a rack to cool completely. Reroll the scraps, and stamp out more cookies, chilling between batches.