For the filling, beat egg yolks in a medium bowl and set aside. In a saucepan, combine 1 cup sugar, cornstarch, and salt. Slowly whisk in orange juice and water until smooth. Cook and stir over medium heat until thickened and bubbly. Reduce heat, stirring 2 minutes longer. Take pan off heat and gradually stir 1 cup hot filling into the bowl with the beaten egg yolks. Return all to the pan, stirring constantly. Bring to a gentle boil, stirring 2 more minutes. Remove from heat; stir in lime juice, orange zest, and 1 tablespoon butter. Pour hot filling into pie crust.
For the meringue, beat egg whites with a mixer until foamy. Add cream of tartar, then beat on medium speed until soft peaks form. Gradually beat in sugar 1 tablespoon at a time on high until stiff peaks form. (Test by turning the beater upside down. If the peak doesn’t wilt when returning beater to an upright position, then it’s ready.) Spread meringue evenly over hot filling, sealing edges all the way to the crust.