Combine the graham cracker crumbs and sugar in a mixing bowl, stirring until evenly distributed.
Pour in the melted butter and mix with a spatula until the crumbs are coated and hold together when pressed.
Press the crumb mixture firmly into the bottom and up the sides of a pie dish, creating an even crust. Bake in a preheated 350°F oven for 8-10 minutes until fragrant and lightly toasted.
While the crust bakes, whisk the eggs in a bowl until frothy and slightly bubbly, about 1-2 minutes.
In a separate bowl, mix the sweetened condensed milk, lime juice, and lime zest until smooth and well combined.
Gradually pour the lime mixture into the whisked eggs, whisking constantly to prevent curdling and ensure a smooth custard.
Pour the filling into the pre-baked crust, smoothing the top with a spatula to remove air bubbles.
Bake the pie in the 350°F oven for about 15 minutes, or until the edges are set and just beginning to pull away from the crust.
Remove the pie from the oven and let it cool completely on a wire rack, then refrigerate for at least 4 hours or overnight to set the filling.
Serve the chilled Key Lime Pie topped with whipped cream or meringue if desired, and enjoy the perfect balance of tartness and sweetness.
