In a large-sized skillet, heat the olive oil over medium flame.
Put the sliced chickent to the skillet and season it with cumin, garlic powder, chili powder, paprika, onion powder, salt and pepper. Cook until the chicken is no longer pink and well cooked, it may take around 5-7 minutes.
Add sliced onions and bell peppers ot the skillet. Cook until the vegetables turn tender for around 3-4 minutes.
Lightly grease a separate skillet with a bit of olive oil or cooking spray over medium flame.
Put one tortilla in the skillet. On one half, add some cheese, then a great amount of chicken fajita filling, and additional layer of chesse as topping. Fold the tortilla over to make half-moon shape.
Cook each side for around 3-4 minutes, or until the cheese ais melted and tortilla turns golden brown. Gently, flip the tortilla and cook for more 2-3 minutes from the other side.
Take the quesadillas out from the skillet and allow it cool for a minute before portioning it into wedges. Follow the similar steps for remaining tortillas and fillings.
It's time to serve the quesadillas. You can serve them with guacamole, salsa, sour cream or pico de gallo.