In a medium bowl, soak gelatin in cold water for 5 minutes.
Add boiling water, stirring until gelatin dissolves.
To 3 tablespoons of the orange juice add the orange and lemon zest; set aside for 5 minutes.
Strain the zest out of the orange juice and discard the zest. To the gelatin add all of the orange juice, sugar, lemon juice and salt. Stir until well blended and set aside to cool.
Pour cooled mixture into a 4-cup mold which has been rinsed in cold water. Cover and refrigerate to congeal.