Combine finely diced onion, ground beef, breadcrumbs, egg, garlic powder, salt, pepper, parsley, thyme, oregano, 1 tablespoon of ketchup and Worcestershire sauce in a bowl using your hands until just combined. Be careful not to over mix it.
In another bowl, combine the remaining ketchup with the mustard. Set this to the side.
Preheat the air fryer to 375 F / 190 C.
Cover the air fryer sides and bottom with a piece of parchment paper, and add the ground beef mixture. Use a spatula or spoon to shape it into a round loaf.
Air fry the meatloaf for about 25 minutes.
Use a spoon to coat the meatloaf with the ketchup and mustard glaze, and air fry for another 10 minutes.
Optionally, you can use a meat thermometer to ensure that the meatloaf is perfectly cooked.
Remove the meatloaf from the air fryer, and leave it to rest for about 10 minutes before you slice and serve it.