Preheat and prepare the vegetables

• Preheat the oven to 200 °C (400 °F) and line a large baking sheet.
• Chop the red onion, red bell pepper, green bell pepper and chicken breast into strips.

Season and bake the fajita filling

• Add the onion, peppers and chicken to the baking sheet.
• Drizzle with the avocado oil and sprinkle over the fajita seasoning.
• Mix well so everything is coated, then bake until the chicken is cooked through.

Build the quesadillas

• Warm the oil in a nonstick pan.
• Place a tortilla in the pan and scatter shredded cheese over it.
• Fold the tortilla over and flip until the cheese is melted and the tortilla is browned a little.

Fill and serve

• Remove the quesadilla from the pan and open it up.
• Add the fajita filling inside and serve.