Preheat your air fryer to 390°F (200°C) for about 5 minutes.
In a large mixing bowl, combine the trimmed green beans, olive oil, minced garlic, salt, black pepper, and crushed red pepper flakes (if using). Toss until the green beans are evenly coated.
Place the seasoned green beans in the air fryer basket in a single layer. You may need to work in batches depending on the size of your air fryer.
Air fry the green beans for 8-10 minutes, shaking the basket halfway through for even cooking. Cook until they are tender and slightly crispy.
Once cooked, remove the green beans from the air fryer and transfer them to a serving dish. While they are still hot, sprinkle the grated Parmesan cheese over the top, allowing it to melt slightly.
Drizzle with lemon juice and toss gently to combine. Garnish with fresh parsley before serving.
Notes
Feel free to adjust the amount of crushed red pepper flakes to your spice preference.