The oven must be preheated to 350°F (175°C) and a 9-inch pie dish must be greased with butter or cooking spray before baking.
Add the graham cracker crumbs, cinnamon, sugar, and butter to a medium bowl and mix well. Mix everything until well combined.
In a greased pie dish, press the mixture firmly and evenly into the bottom. Bake for 10 minutes in a preheated oven. Filling should be allowed to cool completely before it is filled.
Set aside the egg whites after beating them until stiff peaks form. Grate lime peel (lime zest), lemon juice, key lime juice, sugar, and sweetened condensed milk together in a separate bowl.
All ingredients should be mixed together. The egg whites should be gently folded in. Using a spatula or spoon, spread the filling evenly over the cooled crust.
The edges should be lightly golden brown after baking for 25-30 minutes. It should be allowed to cool before whipped cream is added.
To make soft peaks, beat heavy whipping cream and vanilla extract together in a large bowl. Be sure to beat the mixture until stiff peaks form after adding the powdered sugar.
After the pie has cooled, spread the whipped cream evenly on top and refrigerate for at least two hours.