Step #1 In a large bowl let the beans soak in enough cold water to cover them by 2 inches for 1 hr & drain them.
Step #2 In a large heavy saucepan simmer the beans in enough cold water to cover them by 1 inch, uncovered, adding more water as necessary to keep the beans barely covered, for 1 to 2 hrs, or until they are tender.
Step #3 Add the salt and simmer the beans for 5 mins.
Step #4 While the beans are cooking, until the vegetables are softened, the bell peppers, stirring, & cook the mixture, add the tomato paste, & the cumin in the oil over moderately low heat, in a heavy skillet cook the onion, stirring, the garlic, for 2 mins.
Step #5 Stir the vegetable mixture into the beans, & let simmer the mixture, add the vinegar & salt & pepper to taste, for 15 mins, stirring every once in awhile, or until it is thickened to the desired consistency.
Step #6 The beans may be prepared up to this point 2 days in advance, kept covered & chilled, & reheated, adding extra water if necessary.
Step #7 Transfer the beans to a serving bowl & Sprinkle top them with the scallion & the coriander.