Exists in two main variations: A 求肥-like variation, and one where 味噌 pasted is piped into a hollowed out ゆず. The latter, I think, makes for a very nice 八寸!
Stuffed ゆず
Take a ゆず (or Amalfi lemon) and scoop out. Keep the lemon pulp to strain off some juice.
Blend together:
200 gr 味噌
100 gr brown sugar
50 gr lemon juice
40 gr walnuts
Fill lemons to ¾
Steam for 1 hour
Dry for 1 month (but check every now and then, lest it dries out too much