Prepare the Crust: If using a store-bought crust, follow the package instructions for baking. If you're making your own, bake your pie crust until golden and let it cool.
Mix Sugar and Lemon: In a saucepan, combine 1 cup of sugar, 1/2 cup of lemon juice, lemon zest, and salt. Cook over medium heat while stirring until the sugar dissolves.
Temper the Egg Yolks: In a separate bowl, whisk the egg yolks. Slowly add a bit of the heated lemon mixture to the egg yolks, whisking continuously, to temper them and prevent curdling.
Combine and Thicken: Pour the tempered mixture back into the saucepan. Cook while stirring continuously until it thickens (about 5–7 minutes). Remove from heat.
Dissolve Gelatin: In a small bowl, combine the gelatin and cold water. Let it sit for a minute, then whisk it into the thickened lemon mixture until fully dissolved. Allow it to cool.
Beat the Egg Whites: In a clean, dry bowl, beat the egg whites until stiff peaks form. Gradually fold this into the cooled lemon mixture, taking care not to deflate the egg whites.
Add Whipped Cream: Gently fold in the whipped cream until everything is smoothly combined.
Fill the Crust: Pour the lemon filling into the cooled pie crust. Smooth the top and refrigerate for at least 4 hours or until set.
Serve: Slice and serve chilled, garnished with extras if desired.