Heat olive oil in a large pot over medium heat.
Add diced onion and sauté until translucent.
Stir in minced garlic and cook for another minute.
Add diced bell pepper and cook until softened.
Pour in the can of diced tomatoes and mix well.
Add chicken or vegetable broth and bring to a boil.
Stir in black beans, cumin, chili powder, salt, and pepper.
Reduce heat and let the soup simmer for 20 minutes.
Adjust seasoning to taste.
Serve hot, garnished with tortilla strips, avocado, cilantro, and cheese.