First, preheat your air fryer to 375°F (190°C) for about 5 minutes.
While the air fryer is heating, trim the ends off the Brussels sprouts and remove any yellow or brown outer leaves. Cut each sprout in half.
In a large bowl, mix the halved Brussels sprouts with olive oil, sea salt, black pepper, lemon zest, minced garlic, and balsamic Vinegar. Ensure all sprouts are evenly coated.
Once the air fryer is preheated, add the Brussels sprouts to the tray or basket, leaving some space between them for proper air circulation. Depending on the size of your fryer, you may need to cook in batches.
Cook for about 15 minutes, shaking the basket or stirring the sprouts halfway through to ensure even cooking.
Use a fork to test a sprout for doneness; it should be tender and the outsides nicely browned and crispy. If needed, cook for an additional 2-5 minutes.
Once done, remove from the air fryer, garnish with optional Parmesan cheese, and serve as a side dish or enjoy as a healthy snack.