Preheat the oven to 175°C (350°F).

In a medium bowl, combine graham cracker crumbs and sugar.

Stir in the melted butter until evenly mixed.

Press the crumb mixture into a 9-inch pie pan, covering the bottom and sides evenly.

Bake the crust for 8–10 minutes, then let it cool completely.

In a large bowl, mix sweetened condensed milk, sour cream, and lemon juice until smooth and fully combined.

Pour the filling into the cooled crust and spread evenly.

Bake for 10 minutes, then remove from oven and cool to room temperature.

Cover and refrigerate the pie for at least 4 hours, preferably overnight.

Before serving, top with whipped cream and garnish with lemon zest or slices if desired.