While preheating, cut the onion into thick slices. Place on a grilling tray (or use thick aluminum foil).
In a small bowl, combine the oil, salt and pepper, garlic powder and Italian seasoning
When the grill is ready, place the sausages on the grill and the onions on as well.
Baste the onions with the oil mixture on one side.
Continuously turn the sausages for even grilling
As the onions get soft, try to turn them to the other side in the slice shape. If not, it’s ok that they fall apart, just keep them all near the center of the tray/foil so they don’t fall into the elements.
When the sausages are done cooking and no pink is detectable in the center, remove from the heat or set to the cooler part of the grill.
Open 6 buns and place them on the grill for toasting
When the onions are cooked and the buns are toasted, remove everything from the grill.
To assemble, place one sausage on each bun, top with Dijon mustard if you wish, and pile the onions on! Enjoy!