Combine sugar, corn starch and salt in a large heavy saucepan; mix well. Gradually add water and lemon juice, stirring until mixture is smooth.
Beat egg yolks until thick and lemon colored; gradually stir into lemon mixture. Add butter and cook over medium heat. Stir constantly until thick and bubbly. Cook for 1 more minute, stir constantly.
Remove from heat, and stir in lemon zest. Pour into pie shell.
Top with meringue and bake according to meringue directions. I will be posting Nannys Meringue soon. You could also use Cool Whip or whipped cream, Nanny always had a very nice meringue on top of hers.