Prepare Beans: Drain and rinse the soaked black beans.
Cook Aromatics: In a large pot, heat the vegetable oil over medium heat. Add the chopped onion and garlic, and sauté until the onion is translucent.
Add Vegetables: Stir in the carrots, pumpkin, red and green bell peppers, and tomatoes. Cook for about 5 minutes, until the vegetables start to soften.
Season: Add the cumin, salt, and pepper, and stir well to combine.
Add Beans and Broth: Add the soaked black beans and vegetable broth or water to the pot. Bring the mixture to a boil, then reduce heat to low, cover, and let it simmer for about 1.5 to 2 hours, or until the beans are tender. Stir occasionally and add more water if necessary.
Add Greens: About 10 minutes before the end of cooking, add the sliced collard greens or kale, and the smoked tofu or vegetarian sausage if using.
Final Adjustments: Check the seasoning and adjust if necessary. The stew should be thick and the beans soft.
Serve: Ladle the feijoada into bowls and serve hot.