Step 1

Preheat oven to 350In a heavy saucepan, combine 1 1/3 cups sugar and corn starch; add ReaLemon lemon juice.In small bowl, beat egg yolks; add to lemon mixture.Gradually add water, stirring constantly.Over medium heat, cook and stir until mixture boils and thickens, about 8 to 10 minutes.

Step 2

Remove from heat, Add butter; stir until melted. Pour into prepared pie shell.

Step 3

In a small bowl, beat egg whites with cream of tarter until soft peaks form; gradually add remaining 1/3 cup sugar; beating until stiff but not dry.Spread on top of pie, sealing carefully to edge of shell.

Step 4

Bake 12 to 15 minutes or until golden brown.Chill before serving.