If you were a Catalan cowboy, you would roast the unpeeled onions in the coals without wrapping them. This version is easier. Use a mild sweet onion hybrid of the Yellow Granex type: Maui (Hawaii), Vidalia (Georgia), or that European onion transplanted to Washington State, the Walla Walla Sweet.
If you are baking or spit-roasting meats, quarter a few of these onions and put under the meat. All the juices will drip down onto them, the fire will cook them, and then you will want to th