Placing the root of the onion on the cutting board, slice off the top of the other side.
Carefully using your knife or a spoon, core out the middle until you are left with a cup shape.
Preheat your grill to medium heat (about 300F) for direct cooking.
Add your onions with the cup side facing down towards the heat. Let cook for 2-3 minutes until the edges are caramelized.
Next, flip the onions over and add a little olive oil into the cup along with the cubed swiss cheese.
Let cook for 10 minutes uncovered.
Next, cover the onion tops with foil or a fire resistant pan.
Add some cooler charcoal (ashy coals) to the top and let cook for another 10 minutes or until the cheese is melted and the onions are soft.
When done, pull off and let cool for 2-3 minutes.
Slice and serve up with your steak!