In a medium saucepan, combine sugar, cornstarch, lime zest, salt, and limeade. Cook over medium heat, stirring constantly, until the mixture thickens and boils. Boil for 1 minute, then remove from heat and stir in butter.
Pour the mixture into the pre-made graham cracker crust and spread evenly.
In a medium bowl, beat the egg whites until foamy. Add cream of tartar and beat until soft peaks form. Gradually add the 1/4 cup of sugar and continue to beat until stiff peaks form.
Spread the meringue over the top of the pie, making sure to completely cover the filling. Bake the pie in a preheated 350°F oven for 12-15 minutes, or until the meringue is golden brown.
Cool the pie before serving.
Interesting Facts
Limeade pie is a classic American dessert that dates back to the early 20th century.
It is a popular treat in the Southern United States.
Limeade can be made with fresh limes, or with a commercially-prepared limeade concentrate.