In a large bowl, add the Brussels sprouts, olive oil, garlic, lemon juice, lemon rind, chilli flakes, salt and pepper, and mix well.
Evenly spread the Brussels sprouts mixture in the air fryer and air fry for 8-10 minutes. Remove from air fryer, toss the Brussels sprouts and air fry for an additional 5–10 minutes or until the sprouts are golden-brown in colour.
Remove from the air fryer, toss the Brussels sprouts with the Parmesan cheese and serve.