Preheat the air fryer to 380°F for 5 minutes while you prep the chicken.
Pat chicken thighs completely dry with paper towels and tuck a little zest under the skin; brush skin lightly with 1 tablespoon oil.
Season both sides with 1 teaspoon kosher salt, 1.5 tablespoon lemon pepper, 0.5 teaspoon garlic powder, and 0.5 teaspoon onion powder, pressing rub onto skin.
Arrange thighs skin-side up in a single layer in the air fryer with space between pieces and cook at 380°F for 10 minutes.
Flip thighs skin-side down, increase temp to 400°F, and cook 8–12 more minutes until skin is golden-brown and an instant-read thermometer reads 165°F near the bone.
Remove to a rack, brush with melted butter if using, squeeze remaining lemon half over top, rest 5 minutes, then sprinkle parsley and serve.