Prep the broccoli: Rinse and dry thoroughly. Cut into medium florets, about 1.5-inch pieces. Peel the stem if it’s thick and slice into coins or sticks. Drying well is key for browning.
Preheat the air fryer: Set to 390–400°F (200°C). A hot basket helps crisp the edges fast.
Season: In a large bowl, toss broccoli with olive oil, minced garlic (or garlic powder), 1/2 teaspoon salt, and several grinds of black pepper. Add the zest of half the lemon.
Air fry in a single layer: Arrange broccoli in the basket without cramming. Work in batches if needed. Cook 6–9 minutes, shaking halfway, until the florets are browned and crisp at the tips and the stems are tender.
Finish with lemon and Parmesan: Return broccoli to the bowl. Squeeze on 1–2 teaspoons fresh lemon juice, sprinkle with Parmesan, and toss. Taste and adjust with more salt, pepper, or lemon.
Serve hot: Add extra Parmesan and a pinch of red pepper flakes if you like some heat. Serve immediately for best texture.