Preheat your oven to 350 degrees. Using a 9 inch tart pan or a 9n inch pie dish, lightly spray with cooking spray. Set aside.
In a medium-sized bowl, combine the graham cracker crumbs, melted butter, and sugar. With a rubber spatula, stir until all the graham cracker crumbs are combined with the melted butter. You should be able to squeeze the mixture and have it stick together.
Transfer the mixture to the prepped pan and press down firmly with your hand or a flat bottom of a cup. Make sure to get the side crevices of the pan.
Bake for 12 minutes. Make the filling while the crust is baking.
For the filling
In a medium size bowl, combine the lime zest, lime juice, sour cream and sweetened condensed milk and lightly whisk until you have a smooth and creamy mixture.
Pour the filling on top of the crust and bake for 10-11 minutes. The filling is done when the mixture will be slightly jiggly in the center, but the sides and edges will be firm.
Let the pie cool for 10-15 minutes before transferring to the fridge to set up for at least two hours. (I set mine in the freezer for 30 minutes and it was completely set.)
Once the pie has set, make the whip cream. To make the whip cream, add the cream and sugar to a medium size bowl and using a hand mixer whip the mixture until it form soft peak. I used wilton 1M to pipe the dollops on top.