Slow Cooker Braised Flank Steak with Peppers and Onions

In a 5- to 6-quart slow cooker, combine the onion, bell pepper, tomatoes, chili powder, cinnamon, 1/2 tsp salt and 1/4 tsp pepper. Nestle the beef among the vegetables and cook, covered, until the meat is tender and easily pulls apart, on high for 4 to 5 hours or on low for 7 to 8 hours. Twenty-five minutes before serving, cook the rice according to package directions. Using two forks, shred the beef, then stir it into the cooking liquid. Serve with the rice, and top with the mango and cilantro.