Mix the Nilla Wafer crumbs with the melted butter and sugar. Press the mixture into a 9" pie plate.
Bake the crust for 5 - 6 minutes. Set aside until ready to use.
For the pie
Heat marshmallows, lemon juice, water, and half of the lemon zest over medium heat until the marshmallows melt. Stir frequently.
Remove from heat and place the lemon and marshmallow mixture in a bowl. Refrigerate until cooled and slightly thickened.
Once the mixture is cool, fold in the Cool Whip.
Pour the lemon pie filling into the prepared crust. Top with a little extra whipped topping and the remaining lemon zest if desired.
Refrigerate until the pie has completely set. Serve.
If you would rather make your own whipped topping -Beat together 1 cup of Heavy Cream and ¼ cup Powdered Sugar. Beat until fairly stiff and use in place of Cool Whip in the recipe above. You can add yellow food coloring if you want a more "lemony" look to this pie.