LEMON MERINGUE PIE

Ingredients:
1 cup white sugar
2 tablespoons all-purpose flour
3 tablespoons cornstarch
1/4 teaspoon salt
1 1/2 cups water
2 lemons, juiced and zested
2 tablespoons butter
4 egg yolks, beaten
1 (9 inch) pie crust, baked
4 egg whites
6 tablespoons white sugar