You'll need to peel and section a lemon for this dish, Take care to use only the flesh by removing the skin-like, white membrane from each section.
Combine first 3 ingredients in a large saucepan; bring to a boil. Cook 20 minutes or until tender, stirring occasionally. Remove sweet potatoes from pan with a slotted spoon, reserving cooking liquid. Bringing cooking liquid to a boil; cook until reduced to 1/3 cup (about 12 minutes). Stir in sugar and remaining ingredients. Stir in sweet potatoes; cook 2 minutes or until thoroughly heated.