In a large pot, brown the ground beef over medium heat until fully cooked.
Drain excess fat if necessary.
Add chopped onions, garlic, and bell pepper to the pot.
Sauté until vegetables are soft, about 5 minutes.
Stir in chili powder, cumin, salt, and pepper.
Add diced tomatoes and beans to the pot.
Mix well and bring to a simmer.
Reduce heat to low and let simmer for 20-25 minutes, stirring occasionally.
Taste and adjust seasonings as needed.
Serve hot, garnished with optional toppings.