These have a surprisingly sweet flavor - not "oniony" at all.
6 Medium Yellow Onion
1/4 cup Unsalted Butter
1/4 t Kosher Salt
1 t Sherry Vinegar
1 T Italian parsley
Prepare charcoal, and spread in grill, let them cool down to a medium heat.
With the onions still in their skins, place them on the charcoal grate against the charcoal. Close the lid and cook the onions until very tender, 1-1-1/2 hours. Occasionally swap the positions of the onions for even cooking and turn the blackened skins away from the charcoal. When very tender, teh onions will be blackened in spots all over an a knife blade will slide in and out of each onion like a ripe peach. Some onions may take longer than others.
At this point, to finish cooking the onions, you will need to add more charcoal.
Remove the onions from the grill and let cool completely. Carefully remove the skin from each onion, being careful to leave root ends intact so they hold the layers of the onions together. Cut each onion lengthwise throught he stem and root end.
When the fire is ready, put the cooking grate in place. In a 9x13" heavy duty foil pan over direct medium heat, melt the butter. Carefully add the onions in a single layer and season with the salt and pepper. Using tongs, turn the onions in the butter to coat them.
Slide the pan over indirect medium heat and cook with the lid closed as much as possible, until the onions are very tender and just beginning to brown, 10-15 minutes, carefully turning them once or twice. If desired, to keep the onions warm, cover the pan with foil and let them continue to cook over indirect heat for as long as 30 minutes. Using insulated mitts, remobe the pan from the grill. Splash the vinegar and sprinkle the parselty over the onions. Serve warm.
Makes 4 servings.