Heat ½ tablespoon of olive oil in a large skillet over medium heat. Add the diced onion and bell pepper, then cook for 4–5 minutes until softened.
Stir in the shredded chicken, chili powder, cumin, garlic powder, smoked paprika, salt, and black pepper. Cook for another 2–3 minutes until the chicken is heated through. Remove from the heat and stir in the cilantro, if desired.
Wipe the skillet clean and return it to medium heat. Brush or drizzle the remaining olive oil over the skillet.
Place one tortilla in the skillet and sprinkle about ¼ cup of shredded cheese over half of it.
Spoon about ½ cup of the chicken mixture over the cheese, then add another ¼ cup of cheese.
Fold the tortilla in half and cook for 2–3 minutes until the bottom is golden brown and crispy.
Carefully flip the quesadilla and cook for another 2–3 minutes, until the second side is golden and the cheese has melted.
Transfer to a cutting board and let it rest for 1 minute before slicing into wedges. Repeat with the remaining tortillas and filling.
Serve warm with salsa, sour cream, guacamole, pico de gallo, and lime wedges, if desired.
