Florida Key Lime Pie

1 (9-inch) prepared graham cracker pie crust
1 (14 ounce) can sweetened condensed milk
1/4 cup key lime juice
Grated zest from 1 key lime (optional)
2 eggs, separated
1 egg, room temperature
4 tablespoons sugar

Refrigerate graham cracker crust until well chilled. Preheat oven to 350°F. In a medium bowl, combine condensed milk, key lime zest, and key lime juice. Add egg yolks and egg; stir until well blended. Pour into chilled graham cracker crust. In a medium bowl, beat egg whites until stiff peaks form; gradually fold in sugar. Spread meringue over key lime mixture, being careful to spread to edge of pastry to prevent shrinkage during baking. Bake 20 minutes or until meringue is golden brown. Remove from oven and cool completely on a wire rack. Refrigerate before serving. Makes 6 servings.