Add tomatoes and beans: Stir in the diced tomatoes, black beans, kidney beans, pinto beans, chili powder, cumin, oregano, cayenne pepper, salt, and pepper.
Simmer: Bring to a boil, then reduce heat and simmer for 2-3 hours, or until flavors have melded.
Serve: Serve hot, topped with your favorite chili toppings, such as shredded cheese, chopped onions, sour cream, and avocado.
Tips:
For a spicier chili, add more cayenne pepper or a teaspoon of hot sauce.
You can add other vegetables to your chili, such as corn, zucchini, or mushrooms.
For a thicker chili, add a tablespoon of tomato paste or a splash of cornmeal.