Preheat your oven to 425°F (220°C), or 200°C if using a fan oven.
In a small bowl, combine your seasoning ingredients: chili powder, ground cumin, garlic powder, onion powder, smoked paprika, cayenne, dried oregano, and black pepper. Mix these spices well until they are fully blended; this is your homemade fajita seasoning.
On a large rimmed sheet pan, drizzle the vegetable oil or avocado oil. Next, add the sliced chicken, sliced bell peppers, and sliced onion. Sprinkle the fajita seasoning over everything, along with a pinch of salt, then toss it all together until every piece is well coated with the oil and spices.
Roast in the preheated oven for 10 minutes. After that time, carefully flip the chicken and veggies, ensuring they roast evenly. Roast for an additional 5 minutes. It's essential to check the internal temperature of the chicken; it should reach 165°F (74°C).
If you want to add a little char to your dish, place the pan under the broiler for 2 to 3 minutes.
If desired, wrap your flour tortillas in foil and add them to the oven during the last 3 minutes of cooking.
Once everything is cooked, remove the pan from the oven and allow it to cool for a few minutes. Then serve the delicious roasted chicken and vegetables in the warm flour tortillas, topping with fresh lime juice, guacamole, cilantro, and pico de gallo.
