Start by washing and trimming the green beans, removing any tough stems or ends.
Place the green beans in a small bowl and toss them with 1 to 2 teaspoons of olive oil, just enough to lightly coat all the beans. This helps them crisp up nicely during roasting.
Preheat your air fryer to 200°C (390°F) for about 3 minutes. This initial heat jumpstart helps achieve that smoky, crispy edge.
Transfer the coated green beans to the air fryer basket, spreading them out in a single, even layer. Avoid overcrowding to ensure they roast evenly.
Cook the green beans for 8 to 10 minutes, shaking the basket halfway through to promote even roasting and prevent sticking. You should hear a gentle sizzle as they roast.
Check the beans for a slight char and crispy edges—these signs indicate they’re ready. They should be tender inside with a smoky, caramelized exterior.
If you want them extra crispy, roast for an additional 2 minutes, keeping a close eye to prevent burning.
Once done, transfer the green beans to a serving plate. Sprinkle with a pinch of sea salt, freshly grated lemon zest, and Parmesan cheese if using. Toss gently to combine.
Serve immediately to enjoy the crispy, smoky, and vibrant green beans at their best texture and flavor.