Preheat your oven to 300°F (150°C).

In a food processor, combine the unbleached all-purpose flour, icing sugar, salt, grapefruit zest, and fresh thyme. Pulse until well combined.

Add cold cubed vegan butter to the flour mixture in the food processor. Pulse until a rough dough starts to form.

Transfer the dough into a 9-inch fluted tart pan and press it down evenly across the bottom and up the sides.

Bake for 35-40 minutes until the edges are golden brown and the surface is firm.

Let the cookies cool in the pan for about 10 minutes, then cut into 16 equal pieces.

In a mixing bowl, whisk together icing sugar and grapefruit juice until smooth.

Dip the cooled tops of each cookie into the grapefruit icing and place them on a drying rack.

For a second layer, dip again and sprinkle with fresh thyme or pearl sugar while still wet.