Scrub, peel and slice your sweet potatoes 1/4” thick. Boil potatoes in salted water until fork tender, drain and set aside.
Using some butter, grease a 2 quart casserole dish. Cut the peeled bananas into 1/4” slices. In a medium size bowl add the bananas and orange juice, mix to coat. In another small bowl mix together the brown sugar and the cinnamon.
In the bottom of the prepared casserole dish layer 1/3 of the potatoes, then 1/2 of the bananas, sprinkle 1/3 of the sugar mixture and use 1/3 of the butter. Repeat layering reserving 12 slices of bananas for the top. Finish the third layer with the remaining potatoes and the 12 banana slices and the rest of the sugar mixture and butter. If there is any orange juice remaining in the bowl pour it on top.