1. In a food processor, pulse the flour, sugar, and salt until combined.

2. Add the cold butter cubes and pulse until the mixture resembles coarse crumbs.

3. Add the grapefruit zest and thyme leaves, and pulse just until the dough starts to come together.

4. Turn the dough out onto a lightly floured surface and gently knead it a few times to bring it together.

5. Shape the dough into a disk, wrap it in plastic wrap, and refrigerate for at least 30 minutes.

6. Preheat the oven to 350°F. Line a baking sheet with parchment paper.

7. Roll the chilled dough out to 1/4-inch thickness and use a 2-inch round cookie cutter to cut out circles.

8. Place the cookies on the prepared baking sheet, spacing them about 1 inch apart.

9. Bake for 12-15 minutes, until the edges are lightly golden.

10. Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.