- Soak the beans overnight in warm water.
- Strain and dust with baking soda.
- Let stand for 15 minutes.
- Rinse with hot water and rub a few at a time between your fingers to remove the skins (discard the skins).
- Place in strainer and rinse thoroughly for several minutes.
- Put into a large pot along with enough water or chicken stock to cover and bring to a boil, skimming off the foam as it rises.
- Add the onions, tomato, rosemary, garlic, oil, salt and pepper and simmer covered until the beans split; about 90 minutes to 2 hours.
- Serve hot with lemon slices.