In a large bowl, add beef, oil, 2 garlic, oregano, red pepper flakes and salt and mix until well combined.
Make 2 (½-inch-thick) patties from the mixture.
Grease the Air Fryer Basket with cooking spray and then slide inside.
Adjust the temperature of Air Fryer to 350 °F to preheat for 5 minutes.
After preheating, arrange the patties into the greased Air Fryer Basket in a single layer.
Slide the basket into Air Fryer and set the time for 15 minutes.
While cooking, flip the patties once halfway through.
After 14 minutes of cooking, place 1 cheese slice over each patty.
After cooking time is finished, remove the patties from Air Fryer and place onto a plate.
Place 1 lettuce leaf on the bottom of each bun.
Top each with 1 patty, followed by tomato, onion and 1 lettuce leaf.
Cover each with top buns and serve.