Prepare the Mexican chicken marinade and pour it into a sealable bag with the chicken tenders and marinate for 4 hours for the best flavor (a minimum of 2 hours). Timesaver tip: You can also do this step the night before and let them marinate overnight.
Preheat the griddle to medium heat (375 degrees F) while you prepare the veggies.
Slice the tops off the peppers, remove the seeds, and slice into thin even strips.
Next, slice the onion into strips and toss them together in a large bowl.
Add 2-3 tablespoons of avocado oil to the griddle and spread around with the spatula to coat the surface.
Add the veggies first, to one side of the griddle, and cook for several minutes tossing occasionally with the spatula until the veggies start to caramelize. Season, to taste, with additional fajita seasoning. Move the vegetables to the other side of the griddle and turn the heat down to low to allow them to continue to slow cook while you cook the chicken.
Add a little extra oil to the griddle, if needed, and add chicken with the marinade juices to the griddle and cook until the chicken gets a nice golden sear on each side and the internal temperature reaches 165 degrees F with a meat thermometer. Be careful not to over-cook the chicken and dry it out.
Serve with lime wedges, tortillas, and chopped fresh cilantro, if desired.
Notes
Be patient with the griddle as it preheats. It must be HOT. As soon as the peppers and onions hit the flat-top, they should sizzle.
Make sure that your Blackstone is well-seasoned and oiled with a thin layer of oil for the best non-stick surface. Be sure to use an oil with a high smoke point. Avocado oil is my favorite.
Chicken begins to dry out when it's cooked past 165F, so keep an eye on it and promptly remove the pieces from the heat as soon as they reach a safe internal temperature.
Cheese lovers- sprinkle some shredded cheese on top of the peppers to melt right before pulling off the grill