Preheat the oven to 350°F

In a mixing bowl, stir together the graham cracker crumbs and sugar

Add the melted butter and mix until the crumbs are evenly coated and resemble wet sand

Press the mixture firmly into the bottom and up the sides of a 9-inch pie dish

Bake for 8–10 minutes, or until lightly golden and set

Remove from the oven and allow the crust to cool slightly while you prepare the filling

In a large bowl, whisk the egg yolks and lime zest until smooth and slightly thickened

Whisk in the sweetened condensed milk until fully combined

Add the key lime juice and whisk until the filling thickens and becomes creamy

Refrigerate for at least 3 hours, or until fully chilled and firm

Pour the filling into the prepared crust and smooth the top

Bake for 15–17 minutes, just until the center is set but still slightly jiggly

Remove from the oven and let the pie cool at room temperature for about 30 minutes