Preheat oven to 425 degrees F and line 2 large baking sheets with unbleached parchment paper. Set aside.
In a small bowl, combine chili powder, smoked paprika, cumin, oregano, garlic powder, onion powder, salt and pepper. Whisk well.
Place chicken, bell peppers and onion on a baking sheet. Drizzle with oil and sprinkle with fajita seasoning. Using tongs or your hands, toss to coat evenly and then spread in a single layer on 2 baking sheets, so meat and veggies have a greater chance to roast.
Bake for 20 minutes or until chicken is cooked through (internal temperature should be 165 F) or to your liking.
Remove from the oven, drizzle with lime juice and sprinkle with cilantro. Warm up tortillas in a microwave.
Serve chicken fajitas hot in tortillas with your favorite toppings.
Notes
Sodium note: Most of sodium comes from flour tortillas. You can try to find lower in sodium ones.
Store:Refrigerate leftovers in an airtight container for up to 3 days. To reheat, throw on a non-stick skillet and pan fry until warmed through. It will give fajitas an extra char and refresh them.
Different baking sheet: Dark colored baking pan might cook fajitas faster.
Ovens vary: If you have convection oven by default, it will cook fajitas faster as well.