Preheat your oven to 350°F (175°C).

In a bowl, mix the graham cracker crumbs, sugar, and melted butter until it looks like wet sand. Press the mixture into a 9-inch pie dish, covering the bottom and sides evenly.

Bake for 10 minutes, then let it cool.

In a medium bowl, whisk together the egg yolks and key lime zest until thick.

Add the sweetened condensed milk and continue to mix. Finally, whisk in the key lime juice until smooth and creamy.

Pour the filling into the cooled crust and bake for 15 minutes, just until the center is set.

Let it cool completely, then refrigerate for at least 2 hours.