Chop the chicken into small pieces and toss in a bowl with the seasoning powder. Cut the bell pepper lengthwise into 1/4" strips and thinly slice the onion lengthwise. Place vegetables into microwavable cookware with a steam basket and add water to the bottom of the dish, place your chicken and veggies in the basket, cover, and cook for 6 minutes or until the juices of the chicken run clear. No steam basket? Without water, place the veggies on the bottom of a glass container, cover with chicken, a lid, and microwave on high for 10 minutes.
Place the tortillas into a Ziploc bag and microwave on HIGH for about 30 seconds or until warm. To serve the fajitas, spoon the chicken and vegetable mixture onto the centers of the tortillas. Serve immediately with cheese, sour cream or Greek yogurt, and salsa.