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Whole Roasted Onions -- When you slow roast whole onions, they turn from raw, firm and sharp, to sweet, soft, and aromatic.

Whole Roasted Onion Recipe with Vermouth

Valentina K. Wein
This Whole Roasted Onion Recipe with Vermouth is unexpected and so delicious! When you slow roast whole onions, they turn from raw, firm and sharp to sweet, soft, and aromatic.
*Makes 6 whole onions
*Once the onions are roasted, they will keep for a week or so, wrapped tightly in the refrigerator and can be added to all sorts of dishes, as noted above.
5 from 3 votes
Prep Time 10 mins
Cook Time 4 hrs
Total Time 4 hrs 10 mins
Course Side Dish
Cuisine American
Servings 12
Calories 137 kcal


  • 6 large yellow onions (about 3/4 to 1-pound each)
  • 1/2 cup extra virgin olive oil
  • 3 tablespoons extra dry vermouth
  • a few sprigs fresh rosemary, washed & dried
  • a few sprigs fresh oregano, washed & dried
  • 3 tablespoons unsalted butter
  • salt and freshly ground black pepper


  • Preheat the oven to 300°F, and adjust a rack to the center.
  • Do not peel the onions! Slice the root end off of each one, just about 1/2-inch — only enough to create a base so the onions don’t roll around. Then slice about 1-inch off the tip end of each one, and use the knife to mark an “X” on top, going in only 1/2-inch or so. Place them in a 9 x 13 x 2-inch pan, root ends down.
  • Drizzle the onions evenly with about 2 tablespoons of the oil and sprinkle generously with salt and pepper.
  • Place in the preheated 300°F oven, uncovered. After 1 hour, remove them from the oven and drizzle with another 2 tablespoons of the oil, and the vermouth divided among them. Then cover the pan lightly with foil, return them to the oven for 1 more hour.
  • Remove from the oven again and take off the foil. Add about half of the fresh herb sprigs to the pan, surrounding the onions. Then drizzle the onions evenly with the remaining oil and insert about 1/2 tablespoon of butter into the center of each onion and turn the oven up to 350°F. Return the onions, uncovered, to the preheated 350°F oven and roast for another 30 minutes.
  • Remove from the oven and let them cool in the pan. Once they’re cool enough to touch, take off the skins, slice and serve with the remaining fresh herbs.


  • If at any point while the onions are uncovered, they seem like they are becoming too dark (darker than golden), light cover them again with foil.
  • Cooking times may vary, depending on the size of the onions -- just be sure they're very, very soft when they're done.
Keywords best vegetables to roast, vegetarian comfort foods
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