Grease the Air Fryer Basket with cooking spray and then slide inside.
Adjust the temperature of Air Fryer to 400 °F to preheat for 5 minutes.
In a bowl, add the green beans, mushrooms, oil, lemon juice, sage, and spices and toss to coat well.
After preheating, arrange the mushroom mixture into the greased Air Fryer Basket.
Slide the basket into Air Fryer and set the time for 12 minutes.
While cooking, shake the basket after every 5 minutes.
After cooking time is finished, remove the mushroom mixture from Air Fryer and transfer into a serving dish.
Top with fried onions and serve.