Put the macadamia nuts and graham crackers into a food processor and process until crumbly. Add the melted butter and sugar. Pulse until combined. Press into a deep dish 9-inch pie pan and bake at 350°F for 8 minutes.
Beat the egg yolks and sugar until light and fluffy. Add the sweetened condensed milk, key lime juice (1/2 - 3/4 cup depending on how tart you like it), and key lime zest. Stir until combined.
Pour into the pie crust and bake at 350°F for 15 minutes.
Cool completely before topping with whipped cream and key lime zest.