Heat the olive oil in a medium pot over medium heat.
Add the diced yellow onion and red bell pepper, sautéing until the vegetables are softened and translucent.
Stir in the minced garlic, chili powder, and ground cumin, cooking for one minute until the spices become fragrant.
Pour in the chicken broth, tomato sauce, and diced green chiles, then stir to combine.
Place the whole chicken breast into the liquid and bring the mixture to a gentle simmer.
Cover and cook for 15 to 20 minutes, or until the chicken is fully cooked through and easy to shred.
Remove the chicken from the pot, shred it using two forks, and then return the meat to the soup.
Season the soup with sea salt and black pepper to taste.
Ladle the soup into a bowl and garnish with fresh cilantro and sliced avocado before serving.