Add olive oil in a large pot and heat over medium heat. Add the onions, celery and carrot along with a sprinkle of salt. Cook the vegetables until they are soft, about 10-15 minutes, stirring occasionally.
Add the garlic, cumin and red pepper flakes and cook until fragrant, around 30 seconds.
Add the black beans and vegetable broth and increase the heat to medium-high. Bring to a simmer. Adjust the heat to maintain a gentle simmer and avoid a rolling boil. Cook for 30 minutes.
Remove 4 cups of the soup and puree in a blender until smooth. (Be very careful with hot liquids in a blender. Carefully allow the steam to escape.) Add the pureed soup back to the pot of soup. Stir in the cilantro, lime juice, salt & pepper.
Serve with your favorite garnishes!