In a bowl, mix together the ground beef, salt, pepper, and onion powder.
Peel and slice the onion into 1-centimeter (½ inch) rings. Detach the rings from each other.
Take a spoonful of the beef mixture and press it into the bottom of a ring.
Push a cheddar square into the center of the beef.
Seal the top with another spoonful of the beef, pressing it flat.
Repeat with the rest of the rings.
Place the flour, eggs, and bread crumbs into three separate bowls.
Dip a ring into the flour, shaking off excess, then into the egg, the bread crumbs.
Repeat with the remaining rings.
Place in the air fryer basket, spray with oil.
Air fry the rings for 12 minutes at 350 °F. Check the internal temp, flip the rings, spray with oil, and cook at 400 °F for an additional 3-4 minutes or until cooked thru (160F) and golden-brown.