Make the graham cracker crust: In a blender or food processor, pulse the crackers until they turn into fine crumbs. Add the melted butter and sugar and pulse a few more times until well combined.
Bake your crust: Press the crust into your 8 x 8 square pan that is lined with parchment paper and bake at 350ºF for 8 minutes. This helps the pie crust set before adding the filling.
Prepare your pie filling: In a large mixing bowl, whisk the eggs (make sure they are at room temperature) , sweetened condensed milk, vanilla extract, and key lime juice and zest until the creamy filling becomes thick and well combined.
Bake the pie: Bake the bars for 15 minutes at 350ºF. You know when it's done when you touch the edge and it feels set without any residue getting on your finger. When you shake the pan, the middle should be slightly jiggly. It will set completely as it cools.
Let cool then chill before enjoying: Let the bars cool completely before storing in the fridge for at least 2 hours. Chilling longer and overnight helps deepen the flavors of this even more! Garnish with whipped cream and lime slices and serve!