Preheat oven to 350°F. Bake the graham cracker crust for 6-8 minutes. Remove from the oven and let cool.
In a large bowl combine the sweetened condensed milk, sour cream, key lime juice, and lime zest. Using a hand mixer, beat until thoroughly combined. About 1 minute. If you don’t have a hand mixer you can use a whisk and just whisk vigorously. Pour the mixture into the graham cracker crust.
Bake for 10 minutes. Tiny pinhole bubbles will begin to burst on the surface of the pie (hard to see so watch closely). Do not brown the pie.
Remove the pie and let sit at room temperature until warm. Then chill thoroughly before serving.
Garnish with freshly whipped cream and lime slices.