Pepe’s Cafe Key West has the distinction of making the favorite Key lime pie of David Sloan, self-proclaimed Key lime pie expert and author of the Ultimate Key Lime Pie Cookbook. He points out in an interview with Epicurious that rather than just using egg yolks like a classic Key lime pie, "They use some egg white with the condensed milk. It makes it a little fluffier, very nice."
Special equipment: 9-inch pie plate, stand mixer fitted with the whisk attachment (optional
Arrange a rack in the middle of the oven and preheat to 350 degrees.
In a medium bowl, stir together the graham cracker crumbs, sugar, and cinnamon. Drizzle with the melted butter and stir until well combined. Press the mixture evenly onto the bottom and up the sides of a 9-inch pie plate. Bake until set and golden brown, about 10 minutes. Transfer to a wire rack to cool completely. Leave the oven on.
In the bowl of a stand mixer fitted with the whisk attachment, or a large mixing bowl with a whisk or hand mixer, beat the egg whites until they hold stiff peaks. In a large mixing bowl, whisk together the egg yolks and sweetened condensed milk. Add the lime juice and whisk until combined. Gently fold in about 1/3 of the egg whites to lighten the mixture then add the remaining egg whites and fold until just evenly combined. Gently spread the mixture in the pre-baked crust and bake until just set in the center, about 20 minutes.
Transfer to a wire rack to cool completely then refrigerate at least 2 hours before serving. DO AHEAD: The pie can be baked and stored, covered, in the refrigerator, up to 3 days.