Preheat your oven to 350°F (175°C). In a medium bowl, combine the graham cracker crumbs and granulated sugar. Pour in the melted butter and stir until the crumbs are evenly moistened.

Press the crumb mixture firmly into the bottom and up the sides of a 9-inch pie plate. Bake for 10-12 minutes, or until lightly golden and fragrant. Let the crust cool completely on a wire rack before proceeding.

While the crust cools, in a large bowl, whisk together the sweetened condensed milk, fresh lemon juice, and lemon zest until smooth and well combined. The mixture will thicken as you whisk due to the lemon juice interacting with the condensed milk.

Pour the lemon filling into the cooled graham cracker crust, spreading it evenly. Cover the pie loosely with plastic wrap and refrigerate for at least 4 hours, or preferably overnight, until the filling is firm and set.

Just before serving, in a chilled bowl, beat the cold heavy cream and powdered sugar with an electric mixer on high speed until stiff peaks form. Be careful not to overbeat.

Slice the chilled pie and serve with a generous dollop of fresh whipped cream. Garnish with a little extra lemon zest, if desired.