In a large stockpot or dutch oven, heat olive oil under medium heat. Add onions and bell peppers. Sautee for 1 - 2 minutes. Stir in garlic, salt, pepper, and spices.
Add ground beef and cook until browned. Stir in tomato paste, tomatoes, and broth.
Bring to a boil, then reduce heat to low. Cook for 20 - 25 minutes, stirring occasionally.
Top with cheese, sour cream, and avocado if desired.