Cuban Braised Beef

1  28 oz can diced tomatoes
1 1/2 lb flank steak, cut in half
1 large onion, sliced
1 1/2 tsp chili powder
salt and pepper
fresh cilantro

cooked rice

Combine onions, tomatoes, meat, and seasonings.  Simmer, covered, until fork-tender, about 2 hours.  Shred and serve over rice.  Top with sliced mango and cilantro.