Preheat oven to 325 degrees F. Spray a 9-inch pie plate with cooking spray and set on top of a baking sheet for easier handling.

In a medium bowl, combine the graham cracker crumbs, sugar and melted butter , stir until graham cracker crumbs are moistened. (If you melt the butter in the bowl you want to use, it's less dishes and a little easier to combine them all!)

Pour the graham cracker mixture into the prepared pie plate and press evenly onto the sides and bottom to make the crust.

In another medium sized bowl (or wash and reuse the graham cracker bowl), whisk together the lemon juice and sweetened condensed milk.

And in a large bowl, or the bowl of a stand mixer, whisk together the lemon zest and egg yolks on high until pale.

Pour the lemon zest and egg mixture in the sweetened condensed milk mixture and beat until smooth, then pour into the pie crust.

Bake for about 25 minutes, until the edges are set and the center jiggles slightly when the pie is moved.

Cool for an hour on a cooling rack, then refrigerate or freeze for at least 6 hours, depending on preference. Serve with whipped cream or cool whip, if desired.