Heat olive oil in a large pot over medium heat. Add onion and cook until softened, about 5 minutes. Add garlic, cumin, and chili powder and cook for 1 minute more.
Pour in vegetable broth and bring to a simmer. Add black beans, lime juice, salt, and pepper. Stir to combine.
Reduce heat and simmer for 20 minutes, or until flavors have melded.
Use an immersion blender to partially blend the soup, leaving some beans whole for texture. Alternatively, transfer a few cups of soup to a regular blender and blend until smooth, then return to the pot.
Serve hot, garnished with your favorite toppings, such as sour cream, shredded cheese, or chopped cilantro.
Notes
This soup is even better the next day! Store leftovers in an airtight container in the refrigerator.