Combine the ground beef, garlic powder, salt and pepper in a bowl. Mix it all together with your hands. Break the meat into 2 balls. Form uniformly flat patties that don’t bulge in the middle.
Set the air fryer to 350 degrees F (180 degrees C) for 4 minutes. When ready, spray the basket lightly with oil. Set the patties in the basket. Cook for 8-12 minutes (times will vary based on your air fryer and desired degree of doneness. I find that 8 minutes is perfect for a medium-rare burger. Halfway through, baste the burger with butter, then flip it over and baste the other side. Finish cooking.
Butter the buns and lightly toast them on the stovetop, or in the air fryer after the patties are done cooking.
Assemble your burger, dressing it with your desired condiments.
If you wish to add cheese, be aware that it can be pushed off the burger while cooking in the air fryer due to the forced circulating air. For this reason, I only add the cheese during the last 15 seconds of cooking.