I'm going to Frankenmuth tomorrow and will be having lunch at Zehnder's. i will see what I can find out, if anything. I have a cookbook called "From Grandma, With Love" written by Chef John Zehnder, but it is cookies, cakes, brownies, etc. No recipe for the cranberry/orange relish. I agree that it is delish!
Edited to Add: I found it!
Zehnder's Cranberry-Apple Relish
1 lb. Northern Spy apples
1 lb. dark red cranberries
2 cups sugar
2 whole Navel oranges, peel on
1. Wash and core the apples, leaving the skin intact.
2. Freeze the cranberries solid.
3. In a food processor, add half frozen cranberries and half apples and turn to chop speed so that the pieces are about a 1/4" square.
4. Chop the entire pound of apples/ cranberries and place in large mixing bowl and add sugar. Chop the peel-on whole navel oranges to the same consistency and mix into the apples/ cranberries/ sugar.
5. Refrigerate and let set 1 hour before serving.
**This recipes comes from John Zehnder's cookbook "The Flavors of Frankenmuth"