Preheat the oven to 350 degrees F (180 C). To make the crust, mix graham cracker crumbs, melted butter, and sugar together in a medium bowl until well-combined. The mixture will be thick, coarse, and sandy. Press into the bottom and up the sides of a 9” pie pan, and use the bottom of a flat measuring cup or drinking glass to press down the crust, making sure it is very tight and compact. Bake crust for 7-8 minutes, then remove from the oven and set aside to cool while you prepare the filling.

To prepare the pie filling, whisk together the eggs, sugar, sour cream or creme fraiche, and salt in a large bowl. Add the lemon juice and zest, and whisk slowly until mixture is even. Pour filling into crust. Place pie plate on a baking sheet and bake for 25-35 minutes, until the edges of the pie are just set and the center still wiggles slightly when you gently move the baking sheet. Remove from oven and allow to cool completely.

To make the topping, place 2 tbsp. cold water in a small saucepan and sprinkle with gelatin. Set aside for about 5 minutes to soften, then warm mixture over very low heat, just until gelatin dissolves. Set aside to cool. 

In large bowl, using an electric or hand mixer if you have one, beat cream and sugar until very soft peaks form. While still beating, slowly pour in the gelatin mixture. Continue beating until soft peaks form. Using a rubber spatula, spread whipped cream over cooled pie. Refrigerate until ready to serve, at least 1 hour or, loosely covered, up to 1 day.