Preheat a large pot on medium heat. Add 1 tablespoon e.v. olive oil and then the onions and garlic. Sauté until lightly browned, stirring regularly.
Add the cumin seeds and sauté for 1 minute longer, stirring regularly.
Now add the chicken broth, chipotle pepper and salt.
Drain the water from the black beans and add them to the pot. Bring to a simmer and put a lid on the pot and reduce heat to low; gently simmer until the beans are soft (about 2 hours). You may need to add warm water to the pot to keep the beans covered.
Add the tomatoes once the beans are almost soft.
Once the beans are soft you can serve the soup as is puree it.