Wash, deseed and slice all peppers into thin strips. Slice the chicken into long thin strips and place in a big bowl. Remove outside skin of onion and cut in half. Cut onion into thin slices about 2"-3" long and add them to the bowl. Add avocado oil, smoked paprika, cumin, and sea salt and mix until well coated and blended. Add lime juice and black pepper. Mix again. (Can make a day ahead and leave in fridge).
In an iron skillet or griddle pan turn flame on to high heat. Place the fajita mixture on the skillet/pan and cook turning frequently for about 6-8 minutes or until chicken is fully cooked.
Serve with salsa, guacamole, cauliflower rice and/or almond flour tortillas.