Heat the oven for 350°F. Place the graham cracker crumbs in a pie pan and stir in the granulated sugar. Add the melted butter and combine well.
With your fingers spread the crumbs and press them evenly into the bottom of the plate and up the sides. Bake for 8 minutes, then remove the crust and cool completely on a wire rack. Leave the oven on.
While the crust is cooling, make the filling. In a mixing bowl, whisk the egg yolks, then beat in the condensed milk. Beat in the lime juice gradually, whisking all the while until it’s all incorporated and the mixture is thick. Pour the mixture into the pie crust (it doesn’t have to be completely cool). Pour in the filling and bake for 15 minutes until almost set.
While the pie is baking, beat the egg whites with the salt until foamy, using an electric mixer or a standing mixer. While the motor is on, gradually add the confectioner’s sugar one tablespoon at a time, until the egg whites are shiny and form stiff peaks. Cover the filling with the meringue all the way to the crust (having the meringue touch the crust prevents the meringue from shrinking as it bakes.). Use an offset spatula or a butter knife to make swoops and peaks. Bake for 10 to 15 minutes until the meringue is lightly browned and firm.
Cool the pie on a wire rack until completely cool, then refrigerate for at least 3 hours before slicing and serving.
Notes
First of all, there is bottled key lime juice that can save the day in terms of time and effort, unless you are just determined to juice your own limes. Nellie & Joe’s Famous Key West Lime Juice is the brand to reach for. Some folks prefer this bottled juice over using regular fresh limes juiced yourself. It really depends on accessibility, time, and energy.