Preheat the oven to 400 F/205 C
In a small bowl combine all the spices and blend them well with a fork or small whisk.
Wash and slice the bell peppers and any jalapenos you may wish to use. Remove the outer skin of the onion and slice that as well.
Cut the chicken tenderloins (or other chicken) into long strips. And add them to the bowl with the veggies. Or add them all to a bag.
Cut up the garlic and add it to the bowl along with the oil. Add the lid to the bowl and shake it so all the ingredients get coated evenly. Or shake them all in a bag or use tongs to mix them all.
Line a large sheet pan with a silicone mat, parchment paper, or spray it with kitchen spray. Then add the chicken fajitas mixture to the pan and spread them out evenly. Bake them in the oven for 10 minutes then stir. After stirring them, cook them for an additional 10 to 15 minutes until the veggies are soft and the chicken is done. The chicken should be at least 165 F in the center. Use a thermometer or just cut a piece open and as long as there is no pink it is ready to go.
Allow the chicken fajitas mixture to cool for a few minutes while you prep the other ingredients like the cheese or avocado. Take a tortilla and pile up some of the fajitas mixture and top with cheese, avocado, sour cream, lime juice, etc. Enjoy!