Preheat your air fryer to 375°F (190°C) for about 5 minutes.
In a mixing bowl, combine the broccoli florets, olive oil, garlic powder, salt, black pepper, and red pepper flakes (if using). Toss until the broccoli is evenly coated.
Once preheated, place the broccoli in the air fryer basket in a single layer.
Cook for 10 to 12 minutes, shaking the basket halfway through to ensure even cooking. The broccoli should be tender and slightly crispy.
If desired, sprinkle the grated Parmesan cheese over the broccoli during the last minute of cooking to allow it to melt slightly.
Carefully remove the broccoli from the air fryer and serve immediately.
For extra flavor, consider adding lemon juice or zest after cooking.
Store any leftover broccoli in an airtight container in the refrigerator for up to 3 days and reheat in the air fryer before serving.