Wash the beans and soak overnight in 3 quarts of water. Cook in the same water with 3/4 of the onion, garlic, salt to taste and one tablespoon of oil. When soft, blend in their own juice and strain. Cut the tortillas into small squares and fry in lard until golden. Drain and remove excess grease. Roast the tomato, peel and blend with the remaining onion, oregano, and salt. Fry the tomato puree in one tablespoon oil until thick. Add bean broth and bring to a boil. Serve in bowls. with a handful of fried tortillas. Makes 6 servings.