Combine the flank steak, water, garlic, carrot, onion, and bell pepper in a large pot and bring to a boil over high heat.
Reduce the heat and simmer covered for 2 hours.
Remove the meat and allow to cool, reserving 1/2 cup of the cooking liquid.
Pound the meat with a mallet or back of a large knife to separate it onto stringy fibres.
Combine with the sofrito, reserved broth, peas, pimientos, salt, and pepper in a large skillet and cook over high heat for 5 minutes, stirring frequently.
Serve with white rice.