Directions:

Mix 1 cup sugar, cornstarch, and salt in a saucepan. Gradually stir in water.

Cook over medium heat, stirring, until boiling. Boil for 1 minute, remove from heat.

Whisk half of the hot mixture into the egg yolks, then return to the saucepan, stirring constantly. Cook until thickened.

Stir in lemon juice, zest, and butter. Cool until warm.

Preheat oven to 325°F (163°C).

Beat egg whites and cream of tartar to soft peaks. Gradually add 1/2 cup sugar, beat to stiff peaks.

Fold egg whites into lemon filling. Pour into pie crust.

Bake 25-30 minutes until set. Cool on a wire rack.

Chill for at least 4 hours before serving.