Place wedges and microwave water in a covered microwave-safe dish with a vent. Microwave on HIGH for 4 to 5 minutes until the outside is slightly tender but centers remain firm, then drain and spread on a rack for 8 minutes to steam dry.
Pour buttermilk into a shallow dish. Mix flour, cornstarch, paprika, onion powder, garlic powder, salt and pepper in another dish.
Dip each wedge in buttermilk, let excess drip away and press into the seasoned flour. Set on a plate and let the coating hydrate for 5 minutes.
Preheat a 6-quart air fryer to 390°F for 3 minutes. Mist or brush wedges gently with the measured oil until no loose dry flour remains, then arrange 8 wedges in one layer in the basket.
Air fry for 9 minutes, turn carefully with tongs and cook for 7 to 9 minutes more until the crust is browned and the thickest potato center is tender. Transfer to a rack.
Repeat with the remaining 8 wedges. Serve 4 wedges per portion, refreshing the first batch in the empty basket for 1 to 2 minutes if desired.