1 lb boneless beef chuck
1 cup water
1/4 medium onion
1 garlic clove
1/4 teaspoon salt
1 tablespoon vegetable oil
1/2 medium onion , chopped
1 green chili pepper , roasted, peeled (or 1 roasted and peeled poblano chili, or 1 canned whole green chili)
2 tomatoes , peeled, chopped (1/2 pound)
1/4 teaspoon ground cumin
fresh ground pepper (to taste)
Place meat in large saucepan. Add water, peppercorns, 1/4 onion and salt to taste. Bring to a boil, reduce heat. Cover and simmer until meat is very tender, about 1 1/2 hours.
Cool meat in broth. Drain, reserving 1/3 cup broth. Shred meat. Mash garlic with 1/4 teaspoon salt to make a paste. Heat oil in a large skillet. Add chopped onion and garlic paste. Cook until onion is tender. Cut chili into short strips. Add chili strips and tomatoes to cooked onion.
Cook 3 to 4 minutes. Add meat, cumin and freshly ground pepper to taste. Cook until meat is heated through. Taste and add salt if needed. Serve in a hot, flour tortilla. Add reserved broth back to machaca to refrigerate leftovers.