Preheat oven to 350°F (180°C).
Scrub sweet potatoes and prick skin all over with fork. Bake for about 40 to 45 minutes until slightly under done. Peel and slice into ¼-inch thick slices.
Place sweet potatoes in a casserole. Sprinkle cranberries, orange zest, sugar, cinnamon, and nutmeg onto sweet potatoes. Pour in orange juice and dot with butter. Bake for 20 minutes.
Remove and serve immediately.