Chop the onion and bell peppers into small pieces; mince the garlic.

In a large pot over medium heat, add a splash of olive oil. Sauté onions and bell peppers for about five minutes until softened. Add garlic and cook for an additional minute.

Stir in the black beans, kidney beans, and diced tomatoes (do not drain). Mix well.

Add chili powder and cumin; stir to combine. Pour in vegetable broth to reach your desired consistency.

Bring to a boil, then reduce heat to low. Cover and simmer for at least 30 minutes to let flavors meld.

Taste and adjust seasoning before serving; garnish with avocado or cilantro if desired.