Preheat oven to 350 degrees.
Rub the chicken breast with oil salt and spices and place it on a baking tray. Roast in the preheated oven for about 20 minutes.
In a large bowl, combine onion, bell pepper, celery, olive oil, salt and pepper and spices. Toss to coat.
Remove the chicken from the oven, slice it, add the veggies to the baking tray and return it to the oven for 15 minutes more, until the chicken is cooked through and the veggies are roasted but still a bit crunchy.
Squeeze juice from fresh lime over fajita mixture and top with avocado and fresh cilantro.