if you are using dry chickpeas wash and let them soak overnight in warm water with the baking soda. Drain the next day. if you are using canned chickpeas, drain and proceed to the next step.
Place the chickpeas in a large pot with enough cold water to cover them. Bring to a boil, removing the scum periodically from the surface. Peel and add the onions. Pour in the oil and simmer, covered, for at least 1 hour or until the chickpeas are tender. Add hot water, if necessary.
Remove the onions with a slotted spoon, mash one of them and return it to the soup; stir well. Add salt and lemon juice and cook for another 15 minutes.
Serve hot, sprinkled with freshly ground black pepper.
NOTES: if you wish you can add 1 teaspoon of cumin and/or 1-2 bay leaves to the soup, while cooking.
