Cut each grapefruit in half. Using a grapefruit knife or other small knife, cut around the outer edge to loosen fruit from shell. Cut between each segment and membrane to loosen it.
In a bowl combine orange sections, banana, cherries, and orange juice. Place grapefruit halves, cut sides up in a baking dish. Mound the orange mixture on top of grapefruit halves. Coat with cooking spray. In a small bowl, combine brown sugar and cinnamon; sprinkle over orange mixture.
Bake about 12 minutes or until grapefruits are warm and topping is heated through.