Saute minced onion in 1 Tablespoon of olive oil. Make a foil sling, place it in the air fryer- this will make it easier to lift the meatloaf out of the pan later. You do not need to line the whole basket with foil.
Use your hands to mix the ground beef, egg, bread crumbs, ketchup, mustard, seasoning salt, pepper, garlic powder, parsley, milk, and sauteed onion. Form this mixture into a loaf about 6 inches long, 4 inches wide, and 2 inches high.
Place the meatloaf onto the foil sling Bake the meatloaf for 15 minutes at 370 degrees. During this cooking time, make the glaze.
In a small bowl, mix together the ketchup, brown sugar, mustard, and garlic powder. Pour the glaze over the top of the meatloaf. Return the meatloaf to the air fryer and bake for another 15 minutes or until a meat thermometer reaches 160 degrees.
When the meatloaf is finished cooking, rest it on the counter for 5-10 minutes before cutting it with a sharp serrated knife.