Prepare the broccoli: Wash the broccoli thoroughly and cut it into evenly sized florets. This ensures that the broccoli cooks evenly in the air fryer and avoids some pieces becoming overcooked while others remain underdone.
Season the broccoli: In a large mixing bowl, toss the broccoli florets with olive oil, minced garlic, salt, black pepper, and red pepper flakes (if using). Make sure each floret is coated evenly in the oil and seasonings. This will help the broccoli crisp up beautifully in the air fryer and infuse it with garlic flavor.
Preheat the air fryer: Set your air fryer to 375°F (190°C) and let it preheat for about 3 minutes. Preheating helps the broccoli cook quickly and evenly while keeping it tender on the inside and slightly crisp on the edges.
Air fry the broccoli: Place the seasoned broccoli florets in the air fryer basket in a single layer, making sure not to overcrowd them. Air fry for 10–12 minutes, shaking the basket or tossing the florets halfway through cooking. Keep a close eye during the last few minutes to achieve your desired crispiness.
Serve the broccoli: Once cooked, transfer the broccoli to a serving dish. If desired, sprinkle with grated Parmesan cheese and squeeze fresh lemon juice over the top for a bright, fresh flavor. Serve immediately while hot and crisp.