Combine graham cracker crumbs, sugar, and melted butter. If the mixture is dry, add an additional 1-2 tablespoons of melted butter to moisten it further.
Press the crust mixture into the bottom and up the sides of a 9-inch springform pan. Chill in the refrigerator while preparing the filling.
Beat cream cheese, sugar, cornstarch, and lime zest until smooth. Add eggs one at a time, then gradually mix in key lime juice.
Pour the filling into the crust and bake at 300°F for 60 minutes or until set. Turn off the oven and let sit for about 25 minutes with the door slightly open.