In a Dutch oven or heavy pot, brown the hamburger just until the meat is no longer pink; drain grease.

Add the onion, bell pepper, garlic, chili powder, cumin, coriander, oregano, and pepper flakes and continue to brown the meat, stirring regularly, for another several minutes.

Next, add the beans, tomato sauce, and diced tomatoes and bring to a gentle boil.

Reduce heat, cover the pot, and simmer for about 1 hour.

Remove the cover and continue to simmer for about 30 more minutes, or until the chili has thickened a bit and has a deep color.

(If the sauce cooks down too quickly, you can add some water, about ½ cup at a time, so the chili doesn’t stick to the bottom of the pot.

Ladle into individual serving bowls and, if desired, top with shredded Cheddar or Jack cheese, sour cream, diced avocados, or sliced green onions.