Preheat your oven to 350°F (175°C).

In a medium mixing bowl, combine the graham cracker crumbs and granulated sugar. Pour in the melted butter and stir until the mixture resembles wet sand. Press this mixture firmly into the bottom and sides of a 9-inch pie pan.

Place the crust in the preheated oven and bake for 8-10 minutes until lightly golden. Remove from the oven and let it cool.

In a large bowl, whisk the egg yolks until thick and pale, about 2 minutes. Gradually add the sweetened condensed milk, whisking until smooth.

Carefully stir in the fresh lime juice and lime zest until fully combined.

Pour the lime filling into the prepared crust, spreading it evenly.

Bake the pie for an additional 15 minutes until the filling is set but slightly jiggly in the center.

Let the pie cool at room temperature for about 30 minutes, then transfer it to the refrigerator to chill for at least 2 hours.

In a medium bowl, whip the heavy cream until soft peaks form. Gradually add the powdered sugar and continue beating until stiff peaks form.

Spread the whipped cream topping over the cooled pie. Garnish with lime zest if desired.

Slice and serve chilled.