Citrus Shortbread
Makes approximately 24 cookies
1 cup (225 g) unsalted butter, melted and cooled slightly, plus more for greasing the pan
6 tablespoons (75 g) granulated sugar
3 tablespoons citrus zest (from 2 oranges, 3 lemons, or 4 limes, or any combination)
¾ teaspoon kosher salt
¼ cup (30 g) powdered sugar
2¼ cups (290 g) all-purpose flour
Position a rack in the center of the oven and heat to 325°F. Butter an 8-by-8-inch metal baking pan and line it with parchment paper, leaving overhang on two sides.
In a large bowl, combine the granulated sugar, citrus zest, and salt. Use your fingers to rub the zest into the sugar until fragrant and slightly damp. Remove 2 tablespoons of the citrus sugar and set aside.
Add the powdered sugar and flour to the remaining citrus sugar and stir to combine, breaking up any clumps.
Add the melted butter and stir gently until just combined. Transfer the dough to the prepared pan and pat it into an even layer (or roll into a log, refrigerate and make sliced variety or press into a square and make cut out variety). Sprinkle the reserved citrus sugar evenly over the top and press gently.
Bake until golden brown and crisp, 50–60 minutes.
Let the shortbread cool completely in the pan on a wire rack. Use the parchment to lift it out of the pan, then cut into rectangles or break into pieces as desired.