Thaw pineapple juice and simmer until it is reduced to ½ c. (or until the total is ⅓ less). Cool.
Soften gelatin in water at least 5 minutes.
Add egg yolks to pineapple juice; add gelatin and ½ c. sugar. Place in double boiler. Cook 10 minutes, stirring often. Remove from heat. Add salt and orange peel. Mix well and chill until mixture thickens, but do