Wash the beans and soak overnight in cold water. Drain the beans and dump into slow cooker.
Place the onions, garlic, scallion and red bell pepper in the food processor.
Add the beef to slow cooker with beans and pour in water. Add the chopped vegetables, grated carrot and ground cumin. Stir well.
Cover the pot and cook on high for 5 hours or until the beans are tender.
Add the plantain, season with salt and pepper and cook for 30 minutes more.
Add chopped cilantro and serve with white rice and hogao.
If using a normal pot: Wash the beans and soak overnight in cold water. Drain the beans and place in a large pot and add the water, beef, chopped vegetables, carrots and cumin. Over medium-high heat, bring the beans to a boil, then cover the pot and reduce the heat to medium-low. Allow the beans to cook until almost tender, approximately 2 hours.
When the beans are almost tender, add the plantains, salt and pepper. Cover and cook for another hour or until the beans are fully cooked. (Add additional water as necessary).
Add chopped cilantro and serve.