Mix sugar and cornstarch in saucepan. Stir in water in gradually. Cook over moderate heat, stirring constantly, until mixture thickens and boils. Boil 1 minute.
Slowly stir half the hot mixture into egg yolks. Then beat egg mixture into hot mixture in saucepan. Boil 1 minute longer, stirring constantly. Remove from heat.
Continue stirring until smooth. Blend in butter, lemon juice, and grated lemon rind.
Pour into baked pie shell. Cover with Meringue, sealing edges of pie. Bake at 400 degrees until a delicate brown, about 8 to 10 minutes. Cool and serve.