Begin by placing graham cracker crumbs into a food processor and pulse until finely ground. Transfer the crumbs to a mixing bowl and stir in the melted butter until the mixture resembles wet sand. Press this mixture evenly into the bottom and up the sides of a 9-inch pie pan to form the crust. Chill in the refrigerator for 15 minutes while preparing the filling.
Meanwhile, zest the limes using a microplane, releasing bright citrus aroma, then juice the limes until you have about half a cup of fresh lime juice. In a mixing bowl, whisk the egg yolks until smooth and slightly thickened. Add the sweetened condensed milk and continue whisking until fully combined and smooth.
Slowly pour the lime juice into the egg mixture, whisking constantly to incorporate. Add the lime zest and whisk until the filling becomes thick and slightly glossy, with a vibrant green hue. Pour the filling into the chilled graham cracker crust, spreading evenly with a spatula.
Place the pie in the refrigerator and chill for at least 4 hours, preferably overnight, to allow the filling to set firmly. The filling will jiggle slightly when shaken gently but will hold its shape once fully chilled.
Once chilled, slice the pie with a sharp knife, pressing down through the crunchy crust and smooth filling. Serve cold, enjoying the crisp crust with the tart, creamy interior that melts on the tongue.
