Put the beans in a bowl, cover with water and leave overnight to soak. Drain well. Place the tomatoes in a bowl of boling water for 30 seconds, then transfer to a bowl of ie water. Drain and peel the skin from tomatoes. Halve tomatoes and remove seeds and finely chop.
Heat 1 Tbsp. oil in a pot and add half the meat. cook over medium heat for 2 minutes, or until weel browned. Remove from pot and repeat with remaining meat.
Add onions to pot with rest of the oil. Saute onions over medium heat for 5 minutes. Add garlic and spices and cook while stirring for an additional 1 minute. Add 2 cups of water and stir. Return meat to pot with beans and tomatoes. Bring to a boil and then reduce heat and simmer, partially covered for 2 hours or until meat is tender. Stir in sugar and vinegar and season with salt. Serve with flour tortillas.