Preheat your oven to 350°F (175°C). Grease an 8×8-inch baking dish or line it with parchment paper.

In a bowl, mix graham cracker crumbs, 1/4 cup sugar, and melted butter until combined. Press into the bottom of the prepared dish.

In another bowl, whisk eggs until frothy. Add grapefruit juice, zest, and remaining sugar; mix well.

Pour the filling over the crust and bake for 25-30 minutes until set and slightly golden.

Allow to cool at room temperature before refrigerating for at least an hour. Cut into squares and serve chilled.