Rinse the beans and soak overnight in enough water to cover plus an inch. Drain and add new water with an inch to cover, 1/2 tsp salt, splash of oil and piece of kombu. Simmer until soft (about one hour) or cook seven minutes in the pressure cooker on second red ring. Cool and remove kombu.
Meanwhile, coat the soup pot bottom with fat of choice and a bit of salt (to help the onions sweat). Add the onion and saute, stirring occasionally, until it gets a little golden. Add celery, carrots and garlic and cook until the garlic just starts to color. Don't cook too long. Add chopped tomatoes.
When beans are done, take just enough of the excess liquid to cover the vegetables, and cook until they're soft. Combine vegetables and beans and cook for 15 minutes with just enough liquid from the beans to make a very thick pottage, rather like mashed potatoes. Cranberry beans become thick and creamy when done. Add more salt, pepper and/or hot sauce if desired.