Remove chicken breasts from refrigerator 30 minutes before cooking to reach room temperature. Pat thoroughly dry with paper towels to remove surface moisture.
Butterfly each chicken breast horizontally without cutting all the way through, then open like a book. Alternatively, place between parchment paper and pound to an even ¾-inch thickness using a meat mallet.
Brush all surfaces of the chicken with olive oil. In a small bowl, combine lemon pepper seasoning, salt (if using), and garlic powder. Apply the seasoning mixture liberally to both sides of the chicken, pressing gently to adhere.
Set air fryer to 380°F and run empty for 5 minutes to reach optimal cooking temperature.
Place seasoned chicken breasts in the air fryer basket with at least ½-inch space between pieces to ensure proper air circulation. Avoid overlapping.
Air fry at 380°F for 6 minutes. Open the air fryer, flip the chicken using tongs, and cook for an additional 5-7 minutes until internal temperature reaches 165°F at the thickest point.
Remove chicken to a cutting board and allow to rest for 5 minutes minimum before slicing to redistribute juices and complete carryover cooking.
Optional: Sprinkle with fresh lemon zest and a squeeze of lemon juice just before serving for brightness.