Peel and chop sweet potatoes into large cubes. In a bowl, blend the brown sugar and thawed orange juice concentrate. Once combined, coat sweet potatoes and place in an oven-safe dish. Cover with pats of butter and sprinkle cinnamon on top and bake in a 350 degree oven for about 1.5-2 hours until potatoes are very soft. *Note: You may substitute granulated sugar for brown sugar if you wish to keep the color of the dish a more bright orange color instead of the darkening it with brown sugar.