Preheat air fryer to 375°F (190°C).
Wash broccolini and pat thoroughly dry to ensure crisping.
In a mixing bowl, combine broccolini, olive oil, salt, pepper, and garlic powder.
Toss ingredients until the florets and stems are evenly coated.
Arrange the broccolini in the air fryer basket in a single layer, avoiding overcrowding.
Cook for 8 minutes, shaking the basket at the 4-minute mark to ensure even browning.
Transfer to a serving plate and finish with lemon juice and parmesan cheese.