Preheat the air fryer: Set to 370–380°F (187–193°C).
Preheating for 2–3 minutes helps the tortilla crisp evenly.
Prep the fillings: If using veggies like peppers or onions, chop them small so they soften quickly. Pat any wet ingredients dry to avoid soggy spots.
Assemble on a flat surface: Lay one tortilla down. Sprinkle a thin, even layer of cheese, leaving a 1/2-inch border around the edge.
Add protein and veggies, then top with a little more cheese. Season lightly with salt, pepper, and a pinch of your chosen spices.
Top and seal: Place the second tortilla on top. Press gently to help the cheese grip the fillings.
Brush the top with a thin layer of melted butter or oil for extra browning.
Air fry the first side: Carefully transfer to the air fryer basket. If your basket has large holes, place the quesadilla on a perforated parchment liner. Cook for 3–4 minutes, until the top is lightly golden.
Flip and finish: Using two spatulas or tongs, flip the quesadilla.
Brush the new top with a little butter or oil. Air fry 2–4 more minutes, until the tortilla is deep golden and the cheese is fully melted.
Rest, slice, and serve: Let the quesadilla sit for 1–2 minutes to set the cheese. Slice into wedges and serve with salsa, guacamole, or sour cream.