Preparation
In a saucepan, mix half of the sugar, salt, and gelatin. Put the egg yolks in a bowl and beat them well. Add the water and lime juice into the beaten egg yolks, and then stir this mixture into the gelatin mixture. Place this over a low heat and cook, stirring continuously, up to the point where it just comes to a boil. Remove it from heat and stir in the grated rind. Refrigerate to chill, stirring it occasionally, until it begins to form a lumpy texture.