Preheat your air fryer to 375°F (190°C) for 3–5 minutes.

In a large bowl, toss the green beans with olive oil, garlic powder, salt, and pepper until evenly coated.

Place the green beans in a mostly single layer in the air fryer basket (work in batches if needed). Cook for 8-10 minutes, shaking the basket halfway through, until tender and slightly crisp on the edges.

Transfer to a serving plate and top with grated Parmesan or lemon zest, if desired. Serve warm.