Boil the flank steak with bay leaves, carrots, 1 onion, and oregano with enough water to cover the ingredients. Cook for 1 to 1 1/2 hours.
Drain and let the meat cool, cut into 2-inch cubes and then shred.
Saute the remaining onion, peppers, and garlic in olive oil until translucent. Deglaze with sherry. Add tomatoes and cumin. Cook for 15 minutes. Add the shredded meat and cook for 1/2 hour. Season with salt and pepper.