Cuban Pork and Black Bean Stew

In a large bowl, pour cool water over the beans, then cover and soak overnight. (Alternatively, put the beans in a large bowl and cover with boiling water to cover them, then soak for 1 hour.) Drain.In a large slow cooker, whisk together the tomato paste, broth, 1 tablespoon zest, juice, cumin, oregano, red pepper and garlic. Add the beans and onion.Sprinkle the pork with salt. Heat the oil in a large skillet over medium-high heat. Cook the pork, turning it over with tongs, until it is browned on all sides, 8 to 10 minutes. Place the pork on top of the bean mixture in the slow cooker. Cover and cook over low heat until the beans are tender and the pork is cooked through and easy to grind, 6-7 hours. Try it and add seasonings if you like. Chop the pork and add to the bean mixture along with the remaining 2 teaspoons of zest. Serve with rice, sour cream and lime wedges if desired.