Position your oven rack in the lower third of the oven, and preheat the oven to 375 degrees F.
PREPARE THE CRUST:
Combine all of the ingredients, press over the bottom and halfway up the sides of an ungreased 9-inch springform pan, and set aside.
PREPARE THE FILLING:
In a large bowl, use an electric mixer to combine all of the filling ingredients for one minute on moderate speed until smooth. Pour the filling into the crumb crust.
Center the pan on the lower rack and bake for 20 minutes. Remove the cheesecake from the oven and cool for 15 minutes. Meanwhile, raise the oven temperature to 475 degrees F.
PREPARE THE TOPPING:
In a medium bowl, whisk together the sour cream and sugar. Carefully spread over the filling, Return the cheesecake to the lower rack and bake for 10 more minutes.
GET READY FOR SERVING:
Transfer the cheesecake to a wire rack, and cool to room temperature. Then cover with foil, and refrigerate 10 to 12 hours (or overnight) before serving.,
To serve, carefully loosen the cheesecake around the sides with a small-blade spatula, release and remove the springform sides, then slide the cheesecake (still on the pan bottom) onto a large platter. Scatter grated lime zest over the cheesecake. Cut into wedges, and serve-- garnished with a key lime slice.
Notes
You should be able to locate graham cracker crumbs in your market's baking aisle. Otherwise, you can crumble twelve 5x2 1/4-inch double crackers.
Key limes aren't always easily available, and they're not so easy to juice. You can look for bottled Key Lime Juice in your market's juice aisle, and that will work just fine.
It's recommended that you use pasteurized eggs for this recipe since the cheesecake is lightly baked.