In a gallon sized zippered bag, add chicken ingredients. Smoosh around to evenly coat. Place in refrigerator to marinate, at least 4 hours (up to overnight).
In a small bowl, combine Pico de Gallo ingredients. Cover and refrigerate, at least 30 minutes (up to overnight).
In a sauce pan over medium heat, add black beans and taco seasoning. Once they start to heat through, use the back of your spoon to slightly smash the beans occasionally, while the continue to cook down. If they start to bubble, reduce heat slightly.
Keep white onions and green onions separate from bell peppers on your cutting board. Drizzle both with oil, salt and pepper.
Preheat griddle (or large saute pan) to high. First add white onions and saute for about 3 minutes, Add marinated chicken (try to keep in one layer). Cook and saute for 8-10 minutes, make sure to flip and turn the chicken pieces. Add bell peppers and incorporate into the onion and chicken mixture. Around the outside of the cooking surface add the green onions (turn once).Continue to cook another 5 minutes (or until chicken is cooked through).
For each diner, make a small plate with a portion of cheese, sour cream, lime juice, and avocado. Use the small fine mesh strainer to drain off the pico de gallo (if you skip this step you will have a soupy mess).
Serve "toppings" plate along with a portion of the chicken fajitas, serving of smashed black beans and 2-4 tortillas.
Notes
Taco Seasoning
Keyword chicken breast, chicken fajitas, flour tortillas, fresh pico de gallo, green bell peppers, marinated chicken, pico de gallo, red bell peppers, white onion