Preheat your oven to 350°F (175°C).
In a mixing bowl, combine graham cracker crumbs, melted butter, and ⅓ cup sugar.
Press the mixture firmly into the bottom and up the sides of a 9-inch pie dish.
Bake the crust for 8-10 minutes or until golden brown.
While the crust cools, whisk together egg yolks and condensed milk in a bowl.
Add fresh Key lime juice and lime zest, mixing until smooth.
Pour the filling into the cooled crust.
Bake the pie for an additional 10 minutes to set the filling.
Remove from the oven and let it cool to room temperature.
Chill in the refrigerator for at least 3 hours before serving.