Preheat your oven to 350°F (175°C). In a medium bowl, combine the graham cracker crumbs, granulated sugar, and salt. Pour in the melted butter and mix until the crumbs are evenly moistened.
Press the mixture firmly into the bottom and up the sides of a 9-inch pie plate. Use the bottom of a measuring cup to compact the crumbs for a more sturdy crust.
Bake the crust for 8-10 minutes until lightly golden. Remove from oven and cool completely on a wire rack before filling.
In a large bowl, whisk the egg yolks until slightly thickened. Add the sweetened condensed milk and continue whisking until well combined.
Gradually add the fresh lemon juice, whisking constantly. The mixture will begin to thicken naturally due to the acid in the lemon juice reacting with the milk proteins.
Fold in the lemon zest, ensuring it's evenly distributed throughout the filling.
Pour the lemon filling into the cooled graham cracker crust, spreading evenly with a spatula. Tap the pie dish gently on the counter to remove any air bubbles.
Cover the pie loosely with plastic wrap, making sure it doesn't touch the filling. Refrigerate for at least 4 hours, though overnight chilling is recommended for best results.
Just before serving, chill a mixing bowl and beaters in the freezer for 10 minutes.
Pour the cold heavy cream into the chilled bowl and beat on medium-high speed until soft peaks begin to form. Add the powdered sugar and vanilla extract, then continue beating until stiff peaks form, about 1-2 minutes more.
Spread or pipe the whipped cream over the chilled pie. For a decorative touch, sprinkle additional lemon zest or add thin lemon slices as garnish.