Season the flank steak with salt and pepper. In a slow cooker, combine the diced tomatoes and their juices with the water, bell peppers, onion, garlic, jalapeño, oregano, cumin and bay leaf. Add the flank steak, cover and cook on high for 5 hours, until the meat is very tender.

Transfer the meat to a cutting board and let rest for 10 minutes. Discard the bay leaf. Stir the olives, capers and 1 tablespoon of the cilantro into the sauce.

Using 2 forks, shred the meat. Return the meat to the sauce to warm through. Season the sauce with salt and pepper. Spoon the meat and sauce into bowls, sprinkle with the remaining 2 tablespoons of cilantro and serve with steamed white rice or warm tortillas.