

Whisk all the ingredients for the glaze together in a glass measuring cup. Set aside.
Slice onion into 1/2" thick slices, keeping rings intact. If using wooden skewers be sure to soak them for 30 mins beforehand. Skewer each onion slice, one per skewer to keep rings in place. Break off excess skewer. Place onion slices in a glass baking dish. Pour 1/2 to 3/4 of the glaze over them. Flip over carefully to coat both sides.
Preheat grill to high and grill each onion for 5 mins, or they begin to soften and have grill marks. Flip and brush or spoon more glaze over them. Cook another 5 mins. Flip carefully as needed and add glaze until it begins to caramelize on the onions.
Take slices off grill and sprinkle tops with sea salt, add more glaze if desired.