In a large pot, heat the olive oil over medium heat. Add the onion and bell pepper and saute until the vegetables are tender, about 3-5 minutes.
Add the garlic and saute until fragrant, about 1 minute.
Add in the black beans, veggie broth, Cuban spice, bay leaf, salt, and pepper. Stir to combine. Cover and bring to a boil.
Reduce heat to low and simmer soup for about 15 minutes, or until the vegetables are very tender.
Once the beans are tender, remove about 2 cups of the soup and blend until smooth (use a blender or an immersion blender). Return the blended portion to the pot to thicken the soup slightly. Stir in the vinegar and sugar (if using).
Serve hot and garnish with fresh green onion or cilantro, fresh avocado slices, and a dollop of Greek yogurt, sour cream, or queso fresco. Enjoy!