Stir together graham cracker crumbs, sugar, and butter in a bowl until evenly combined. Press mixture evenly onto bottom and up side of a 9-inch pie plate. Bake crust on the middle oven rack for 10 minutes, then remove. Place on rack to cook while you mix the filling.
The filling:
While the crust is baking, whisk together the condensed milk, juice, zest and egg yolks in a bowl until combined and thickened.
Pour filling into crust and bake on the middle oven shelf for 15 minutes. Transfer to a cooling rack, and let sit until it reaches room temperature. Then refrigerate for at least 2 hours - the longer the deeper the flavour.
Whip cream and icing sugar until stiff peaks form. Spread evenly on pie just before serving.
Recipe by Chateau Elma at https://www.chateauelma.com/lime-custard-pie-with-whipped-cream