Combine the graham cracker crumbs, sugar, and melted butter in a bowl, mixing until the crumbs are evenly coated and the mixture looks like wet sand. Press this mixture firmly into the bottom and up the sides of a 9-inch pie pan to form the crust. Bake in a preheated oven at 350°F (175°C) for 8-10 minutes until slightly golden, then let it cool completely.
While the crust cools, zest the limes using a grater, avoiding the bitter white pith, and then juice them until you have about half a cup of bright, pulpy lime juice. In a large bowl, whisk the eggs until just blended, then mix in the sweetened condensed milk, lime juice, lime zest, and salt until smooth and well combined.
Pour the lime filling into the cooled crust, smoothing the top with a spatula. Place the pie in the oven and bake for about 15 minutes until the filling is just set but still slightly jiggly in the center. Remove from oven and allow to cool to room temperature, then refrigerate for at least 2 hours or overnight.
Meanwhile, prepare the meringue by whisking the egg whites in a clean bowl until soft peaks form. Gradually add the sugar while continuing to whisk until the meringue is glossy, stiff, and holds firm peaks.
Spread the meringue evenly over the chilled lime filling, making sure to seal the edges to prevent shrinking during baking. Use a spoon or spatula to create peaks and swirls for a decorative effect.
Bake the pie in a 375°F (190°C) oven for about 10-12 minutes until the meringue peaks are lightly golden and crisp. Keep a close eye to prevent over-browning.
Remove the pie from the oven and let it cool completely. Chill for at least 1 hour to allow the meringue to set and the flavors to meld.
Slice the pie with a sharp knife, revealing the creamy, tart filling beneath the crisp, toasted meringue. Serve chilled and enjoy the bright, tangy flavor with every bite.
