Preheat your oven to 350°F (175°C).

Combine graham cracker crumbs, granulated sugar, and melted butter until the mixture resembles wet sand. Press into a 9-inch pie dish and bake for 8 minutes.

Whisk together sweetened condensed milk, fresh key lime juice, sour cream, and lime zest until smooth.

Pour the prepared filling into the cooled crust and spread evenly.

Bake for 18 to 20 minutes until the filling is mostly set but slightly jiggles in the center.

Let it cool at room temperature for 30 minutes, then refrigerate for at least 1 hour before serving.

Slice the pie and serve cold, optionally garnished with lime slices or whipped cream.