carne guisada recipe

3 pounds stew meat (beef chuck or round, cut into 1-inch cubes) 1 tablespoon oil (lard, bacon grease, or vegetable oil) 1 medium onion, diced 1 small green bell pepper, diced (optional) 3 tablespoons tomato sauce (or 1 large tomato, diced) 1 teaspoon garlic powder (or 3 cloves of garlic, minced) 2 teaspoons ground cumin 2 teaspoons salt ½ teaspoon black pepper 2 tablespoons all-purpose flour 1 cup chicken stock (or water) Flour tortillas, rice, or mashed potatoes for serving