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Vegetable Technique: Roasting Onions in Their Skins for Sweetness

Roasting onions in their skins is a simple yet transformative technique that amplifies their natural sweetness while infusing them with a smoky depth. The skin acts as a protective barrier, trapping moisture and flavor inside while the onions caramelize gently in the oven. This method is particularly effective for varieties like red, yellow, or Vidalia onions, known for their inherent sweetness. As the onions cook, their sugars concentrate, resulting in a mellow, almost jam-like texture that’s perfect for spreading on crusty bread or incorporating into dishes like quiches, stews, and sauces. The process is surprisingly hands-off, allowing you to multitask while your oven does the heavy lifting. Plus, there’s minimal cleanup involved since the skins catch most of the mess. Understanding the science behind this technique can help you achieve consistently excellent results, whether you’re cooking for a weeknight dinner or preparing for a weekend brunch.

Notes

The key to this technique is the onions' skin, which acts as a natural wrapper, trapping steam and allowing the onions to cook in their own juices. This gentle cooking process helps convert the onions' complex sugars into simpler, sweeter compounds through caramelization. Common mistakes include not preheating the oven properly, which can lead to uneven cooking, or unwrapping the onions too soon, causing burns from escaping steam. Always use oven mitts when handling hot foil. For storage, roasted onions can be kept in an airtight container in the refrigerator for up to 5 days. They can also be frozen for longer storage. Reheat gently to preserve their texture and flavor.

Steps

  1. 1 Preheat oven to 400°F.
  2. 2 Select medium-sized onions, leaving the root ends intact.
  3. 3 Trim off the stem ends of the onions, about 1/4 inch.
  4. 4 Lightly brush the onions with olive oil, coating the skin evenly.
  5. 5 Wrap each onion individually in aluminum foil.
  6. 6 Place wrapped onions on a baking sheet.
  7. 7 Roast for 45 minutes to 1 hour, or until skins are charred and onions are tender.
  8. 8 Remove from oven and let cool slightly in the foil.
  9. 9 Peel off the skins when cool enough to handle.
  10. 10 Halve or quarter the onions for serving or use.
  11. 11 Optional: Squeeze roasted onions to extract their sweet, caramelized insides.

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