Preheat oven to 350 degrees.
In a large bowl, stir graham cracker crumbs, sugar, and melted butter together until well coated and moist. Pour into a glass pie plate and press into an even layer across the bottom and up the sides as high as they can possibly go. Press well. Bake 8 minutes. Set aside to cool.
As the pie crust bakes, make the filling: whisk sweetened condensed milk together with the egg yolks, lemon zest, and lemon juice until smooth. Set aside to thicken, about 3 minutes.
Pour as much filling as possible into crust without going over the edges. You may have some filling left over. This is normal! But the thickening of the filling should help get nearly all of it. I had 1/4 cup remaining.
Carefully transfer to the oven and bake 25 minutes or until center is set and doesn't jiggle.
Remove from oven, cool to room temperature and refrigerate.
When you are ready to serve, remove pie from fridge and cut into 8 or 10 slices. Sprinkle each slice with a thin layer of granulated sugar. Using a kitchen torch or broiler, melt the sugar over top each slice of pie. Cool 1-2 minutes before topping with whipped cream and serving.