Preheat oven to 350°F and line baking sheets with parchment paper.

In the bowl of your stand mixer, cream together the butter and 1 cup of sugar.

Add 1 tablespoon of the grapefruit zest and the juice. Mix.

Add the egg and mix for about two minutes, being sure to scrape down the sides.

Add the flour, cornstarch, baking powder, soda, and salt. Mix until almost combined.

Add the coconut flakes, and by hand, stir them evenly into the dough.

On a plate, add the 1/3 cup sugar and 2 tablespoons grapefruit zest. Rub together to evenly combine.

Using a cookie scoop, scoop out about 1 1/2 tablespoon of dough and roll into a ball. Roll the ball in the sugar-zest mixture and place on baking sheet. Repeat with remainder of dough.

Once on the baking sheet, slightly flatten the balls to take away the roundness of them.

Bake for 8-10 minutes. Remove from the oven and set for 2-3 minutes before transferring to a cooling rack. Enjoy!