- 1/2 cup (1 stick) unsalted butter, room temperature, cut into pieces, plus more for pan
- 1 tablespoon finely grated grapefruit zest
- 1 teaspoon vanilla extract
- 1/3 cup plus 1 cup powdered sugar
- 1 cup all-purpose flour
- 1/2 teaspoon kosher salt, plus more
- 2 tablespoons fresh grapefruit juice
- Himalayan pink salt, dried hibiscus flowers, red sprinkles or sanding sugar, dried rose petals, and/or cracked pink peppercorns (for serving; optional)
- A 9-inch springform pan
- Lightly butter pan. Pulse grapefruit zest, vanilla extract, 1/2 cup butter, and 1/3 cup powdered sugar in a food processor until smooth and homogenous. Add flour and 1/2 tsp. kosher salt; pulse just to combine. Press dough evenly into prepared pan, smoothing top with a flat-bottomed glass or measuring cup. Chill until firm, about 1 hour.
- Preheat oven to 350°F. Prick shortbread all over with a fork 1″–2″ apart, and bake until edges are golden and center is pale but firm to the touch, 15–18 minutes.
- Remove band from pan and immediately cut shortbread into 16 wedges. Let cool.
- Whisk grapefruit juice, a pinch of kosher salt, and remaining 1 cup powdered sugar in a small bowl until smooth. Spread a thin layer of icing over shortbreads with a small offset spatula, leaving a thin border of crust exposed. Top as desired. Let sit 10–15 minutes to allow glaze to set. Retrace cut marks.
- Dough can be pressed into pan 1 day ahead. Cover and chill.