Heat the avocado oil over medium heat in a heavy bottom dutch oven. Add in the diced onion, bell pepper, and garlic. Sauté until soft, about 8 minutes.
Add in the diced chicken, season with salt and pepper, and cook until the chicken is browned on all sides. add in the tomatoes, capers, oregano, and basil. Simmer, uncovered, until the chicken is cooked through. 10-15 minutes.
Season with salt and pepper to taste. Serve with a side salad, zucchini noodles, or spaghetti squash.