Combine the graham cracker crumbs with melted butter in a bowl, mixing until the crumbs are evenly coated and resemble wet sand. Press this mixture firmly into the bottom and up the sides of a 9-inch pie dish to form the crust. Chill in the freezer while preparing the filling, about 15 minutes, to help it set and prevent sogginess.
In a large mixing bowl, whisk the eggs until they are smooth and slightly frothy. This helps incorporate air and ensures a silky custard.
Add the sweetened condensed milk, lime juice, and lime zest to the eggs, whisking continuously until the mixture is smooth, thick, and slightly pale in color. The aroma should be bright and citrusy.
Pour the lime filling into the chilled graham cracker crust, smoothing the top with the back of a spoon or spatula for an even surface. Place the pie on a baking sheet to catch any overflow during baking.
Bake the pie in a preheated oven at 350°F (175°C) for about 15 minutes, or until tiny bubbles form around the edges and the center jiggles slightly when gently shaken. This indicates it’s just set and ready.
Remove the pie from the oven and let it cool to room temperature on a wire rack. Once cooled, refrigerate for at least 4 hours or overnight to allow the flavors to meld and the filling to firm up.
If desired, whip the heavy cream with sugar until soft peaks form, creating a light, fluffy topping. Spread or pipe the whipped cream over the chilled pie just before serving for a creamy contrast.
Slice the pie with a sharp knife, revealing the bright yellow custard and crisp crust. Serve immediately, garnished with extra lime zest or a dollop of whipped cream if desired.
