Adapted from The Beekman 1802 Heirloom Dessert Cookbook 
Key limes are tarter than Persian limes (regular limes) but often difficult to find. To make a reasonable facsimilie, use 1/2 cup regular lime juice plus three tablespoons lemon juice to replace the Key lime juice here.
Key Lime Pie
- 10 full graham cracker sheets
- 4 Tablespoons (1/2 stick) butter, melted
- 1/4 cup sugar
- 1 teaspoon grated lime zest
- 1/4 teaspoon salt
- 3 large egg yolks
- 1 can (14 ounces) sweetened condensed milk
- 2/3 cup fresh Key lime juice (about 20 Key limes)
- 3 large egg whites
- Pinch of salt
- 1/4 teaspoon cream of tartar
- 1/3 cup granulated sugar
- 1/4 teaspoon pure vanilla extract
1. To make the crust: Preheat the oven to 350F.
2. In a food processor, pulse the graham crackers until finely ground. Add the butter, sugar, lime zest, and salt and process until well combined. Press the mixture into the bottom and up the sides of a 9-inch tart pan with a removable bottom. (This is easily done by using a flat-bottomed measuring cup and pressing it into the pan.) Bake for 10 minutes, or until crisp and set. (Leave the oven on.)
3. To make the filling: Meanwhile in a bowl, with an electric mixer, beat the egg yolks until fluffy. Gradually add the condensed milk and beat until thick. Beat in the lime juice.
4. Pour the filling mixture into the baked crust and return to the oven to bake for an additional 10 minutes, or until just set. Transfer to a wire rack to cool slightly. Increase the oven temperature to 450F.
5. To make the meringue: In a bowl, wiht an electric mixer, beat the egg whites and salt until foamy. Add the cream of tartar and beat until soft peaks form. Gradually, about 1 tablespoon at a time, add the sugar, beating until stiff, glossy peaks form, adding in the vanilla toward the end. Scoop the meringue onto the lime filling, making swoops with a spatula. Bake for 5 minutes, or until the meringue is set and browned in spots. Cool to room temperature. Serve at room temerature or chilled.