Begin by heating a tablespoon of oil in a large pot over medium heat. Add the diced onion and sauté until it becomes translucent and slightly browned, about 5 minutes. Stir in the minced garlic and cook for an additional 30 seconds until fragrant.

Once the garlic is aromatic, pour in the vegetable broth and add the enchilada sauce, stirring to combine. Next, add the black beans, diced tomatoes, and masa harina, whisking thoroughly until there are no lumps.

Increase the heat to medium-high and bring the mixture to a gentle boil. Stir occasionally to prevent sticking and ensure even heating.

Once boiling, reduce the heat to low and simmer the soup uncovered for 10 minutes. Stir occasionally, checking the consistency.

After simmering, remove the pot from the heat and stir in the lime juice, chili powder, cumin, and salt. Taste the soup and adjust the seasoning as needed.

Ladle the steaming soup into bowls and garnish with your favorite toppings, such as crushed tortilla chips or crumbled cornbread for texture. Serve hot.