In a large pot, heat olive oil over medium heat. Add the chopped onion and sauté for about 3-4 minutes until soft and translucent.
Incorporate the minced garlic and diced red bell pepper into the pot, continuing to sauté for another 2-3 minutes.
Add the black beans, diced tomatoes (with juices), chicken broth, cumin, chili powder, salt, and pepper to the pot. Stir well and bring the mixture to a boil.
Once boiling, reduce the heat to low and let it simmer for about 15 minutes to allow the flavors to meld. Stir occasionally.
In a mixing bowl, whisk together the masa harina, baking powder, salt, and cumin.
Add the vegetable oil and chicken broth to the bowl, mixing until the ingredients form a dough-like consistency. If needed, add a bit more broth to achieve the right texture.
Once the soup has simmered, drop spoonfuls of the tamale dumpling dough into the pot, ensuring they are evenly spaced and not overcrowded.
Cover the pot and allow the dumplings to steam in the simmering soup for about 10-12 minutes, or until they are cooked through and fluffy.
After the dumplings are ready, taste the soup for seasoning, adjusting salt and pepper as necessary.
Serve the soup hot, garnished with chopped cilantro and fresh lime wedges on the side.