Rub the chicken with 1 tablespoon of olive oil and then sprinkle with ½ teaspoon of salt and ¼ teaspoon of pepper.
Place the chicken, skin-side down in a pot. Turn the heat on to medium heat and fry the chicken, until most of the fat has rendered out of the skin (about 4 minutes).
Flip and brown the chicken on the other side (another 3 minutes); the chicken does not need to be cooked through. Remove the chicken from the pan and let it cool enough to handle.
Add the onions, garlic and bell peppers to the pan you browned the chicken in. Saute until tender, and the onions start to brown (about 10 minutes).
Add the chili powder, salt, oregano, cinnamon and cayenne pepper. Saute until the spices are fragrant (about 2 minutes).
Add the canned tomatoes along with the juices they're packed into the pot and crush the tomatoes with a wooden spoon. Simmer the chili over medium-low heat for 30 minutes.
While the vegetables are simmering, chop the browned chicken into 1-inch chunks and set aside.
Add the chicken to the chili and continue to cook until the chicken is cooked through (about 5 minutes). Adjust seasonings to taste.
Serve the chicken chili garnished with avocado, red onions, cheddar, and cilantro.