Combine all marinade ingredients (cilantro, garlic, olive oil, lime juice, lime zest, and all seasonings) in a food processor. Blend until ingredients are well combined.
Pour ingredients into a large ziploc bag. (Reserve a couple tablespoons for basting.)
Add chicken breasts to bag. Marinate chicken for 2 hours up to overnight.
When ready to cook, heat grill to medium heat. Remove chicken from ziploc bag with tongs and place onto hot grill.
Cook chicken slowly so it stays juicy. Let grill for 10-15 minutes per side, until cooked through.
Once chicken is cooked through, remove from grill and set aside. Brush with extra marinade and let rest for 5 minutes.
Slice into strips before serving.
In same pan, add another tbsp. of olive oil. Add sliced peppers, cover and cook until slightly brown. Remove cover then add 1/2 tsp. of garlic salt and 1/2 tsp. of chili powder. Stir and cook until peppers are slightly soft. Remove and set aside.
Heat 1 tbsp. olive oil in a large skillet on medium high heat. Add sliced onions. Cover and cook until soft. Remove from pan, set aside.
*Note, you can cook onions and peppers together! We have a couple onion haters in my house so I cook separately ;)
Take warm tortillas and layer them with chicken, peppers, onions, pico, cheese and/or sour cream. Add an avocado slice to your fajita and enjoy!