Wash the broccoli. Cut the florets into bite-sized pieces.
Toss the broccoli florets with the vegetable oil and add the broccoli to the basket of your air fryer in a single layer. Add the lemon half.
Air fry the broccoli and lemon at 375 degrees F for 10 minutes. Open the basket halfway through cooking time. Use tongs to move the broccoli around to make sure it cooks evenly.
Place the air fried broccoli into a clean bowl. Squeeze the juice from the lemon half over the broccoli. Top with Parmesan cheese and serve.