Cook bacon in a Dutch oven over medium heat until crisp. Remove and set aside on paper towels to drain. Crumble bacon when cool enough to handle.
Add sausage to the bacon drippings in Dutch oven and break up as it cooks. As sausage browns, sprinkle with red pepper flakes. When fully cooked, remove sausage and set aside.
Add onions, carrots, celery, and garlic to the Dutch oven and cook for 3 minutes, or until tender. Remove vegetables and set aside in a bowl.
Wipe Dutch oven and return sausage and vegetables to it, along with beans, broth, tomatoes, cilantro, tomato paste, lime juice, cumin, and cayenne. Add bacon and stir to combine. Bring mixture to a boil, reduce heat to low, and simmer uncovered for 10 minutes, or until thickened.
Ladle soup into bowls, top each with sour cream, and garnish with cilantro.