Clean and rinse beans. Dump into slow cooker along with quartered onion and garlic cloves and salt pork. Add water to cover beans by 3 inches. Cook beans on low for 4-6 hours. Check beans after 2 hours and add water if needed. 30 minutes before beans are done, render bacon fat in a large Dutch oven. Once rendered, remove the bacon (save crispy bacon for a salad!) and add onions and bell peppers. Saute for 5 minutes or until onions are translucent and tender. Next, add tomatoes, Worcestershire, chili powder, tomato sauce and cook all together for 10 minutes. Remove onions, garlic and salt pork from slow cooker before adding cooked beans to Dutch oven mixture. Finally, add chopped cilantro, salt, pepper and chili powder (optional); combine and simmer for 30 minutes to meld flavors.