Place in a small cup:
Sprinkle with:
Let stand for 5 minutes to soften. Combine in a medium saucepan:
Bring to a simmer, stirring occasionally to dissolve the sugar. Strain through a sieve into a bowl; discard the zest. Add the gelatin, stirring until it is completely dissolved. Stir in:
Refrigerate the sherbet base until cold, overnight if possible, or quick-chill in an ice water bath.
Pour the base into an ice cream maker and freeze as directed. Serve immediately or transfer to a container with a tight-fitting lid and freeze.