Cut the plaintain into 3/4" chunks and fry for about 2 minutes. Once fried, smash flat. Fry again for about 2 minutes or until crispy. Bake sweet potato fries according to directions on package. Melt the butter and brown sugar in sauté pan. Add rum, burning off the alcohol and add bananas. Toss to heat bananas and coat well. Place the sweet potato fries and plaintains on a plate. Top with the bananas and sauce. Sprinkle with cinnamon.