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    Home»Mediterranean»Balsamic Roasted Red Onions

    Balsamic Roasted Red Onions

    By LilyDecember 19, 20257 Mins Read
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    First baked, then tossed with a sweet balsamic vinaigrette, the silky, sweet, and savory caramelized roasted onions make a comforting vegan and gluten-free side dish.

    Roasted red onions on a platter with a serving spoon.
    Photo Credits: Miriam Novoa

    Why I Love This Roasted Onion Recipe

    • Onions are naturally sweet: Roasting softens the bite of the onions, caramelizing their natural sugars, and a quick agrodolce-style vinaigrette adds tang to every bite.
    • Simple ingredients, big flavor: Just pantry staples, but the results taste like a special-occasion side.
    • Endlessly versatile: It’s vegan and gluten-free, and it goes well with everything!

    I consider the onion, the workhorse of my home kitchen. It’s an indispensable ingredient, but rarely does it take center stage.

    There are exceptions, of course, like French onion soup, or these Greek rice-stuffed onions. One of my favorite ways to showcase onions is to give them the agrodolce treatment, a classic Italian preparation that mixes sweet and savory flavors for a knock-out delivery.

    Typically, agrodolce onions are made with pearl or cipollini onions, sautéed on the stovetop. They’re delicious, but peeling those tiny onions is tedious. Here, I roast quartered red onions instead, then toss them with balsamic vinaigrette while they’re still warm.
    The bright flavor of the red onions pairs perfectly with the sweet-tart vinaigrette. It’s a simple preparation but the results will delight you, I promise! 

    Roasted red onions on a platter.

    How to Make Roasted Red Onions

    These baked onions are practically a foolproof side dish. The key is to roast the onions until they are nicely caramelized and silky but still have a little bite to them. You can prepare the vinaigrette while the onions are in the oven.

    • Get ready. Heat the oven to 400° F. Line a rimmed baking sheet with foil. 
    • Prep the onions. Trim the ends off 6 medium red onions, peel, then cut them into quarters. Arrange on the prepared baking sheet and drizzle with 2 tablespoons extra virgin olive oil. Use your fingers to coat them and season with a pinch of salt and freshly ground black pepper. Roast for 15 minutes.
    • Make the vinaigrette. In a small bowl, combine 1 tablespoon apple cider vinegar, 1 tablespoon balsamic vinegar, 1/4 teaspoon salt, 1/8 teaspoon pepper, and 1/2 teaspoon finely chopped fresh thyme leaves. Slowly whisk in 1/4 cup olive oil, until the vinaigrette is emulsified.
    • Baste the onions. Remove the pan from the oven and brush the onions with about half the vinaigrette, turning them to make sure all sides are coated. Return the onions to the oven and roast until the wedges are nicely caramelized and slightly blackened in spots, another 15 to 20 minutes.The partially cooked quartered red onions being basted with the balsamic vinaigrette on a parchment lined sheet pan.
    • Finish and serve. Gently transfer the onions into a bowl. Don’t worry if they fall apart a little. Drizzle the remaining vinaigrette over them and toss gently with a spoon. Taste and adjust the seasoning with more salt or pepper if needed. Let the onions marinate for about 15 minutes before serving.

    What is Agrodolce?

    Mixing sweet and tart flavors is a hallmark of Italian cuisine. Agrodolce sauce is typically made from a mix of vinegar and sugar or honey or another sweet ingredient such as balsamic vinegar.
    Sometimes the mixture is reduced on the stovetop to thicken it. For this recipe, the sweet and tart elements come together in a vinaigrette, no reduction needed! 

    I use two vinegars to make this vinaigrette—cider vinegar, which has a fresh kick, and balsamic vinegar, which is sweet and syrupy. Together, they have just the right amount of agrodolce.

    A close up of roasted red onions.

    Make it Your Own

    • Change up the shape: Instead of quartering, cut the onions in half crosswise. You may need to roast them an additional 5 minutes, but the pattern of caramelized concentric circles makes for a pretty presentation.
    • Substitute honey: If you don’t have balsamic vinegar in your pantry, simply substitute the same quantity of honey. Use one with robust flavor, like our Italian citrus honey or organic wildflower honey.
    • Add mustard. Stirring a dollop of Dijon mustard into the vinaigrette punches up the flavor.
    • Add fennel. Cut one or two fennel bulbs into wedges and roast them along with the onions. They go well together!

    Perfect Pairings

    You might think of onions as an unusual side, but these silky sweet and sour wedges pair well with lots of dishes. Try them with

    • Pork chops with bay leaf and lemon slices, or salmon piccata.
    • Roasted onions make a great topping for pizza. Try it with our whole-wheat pizza dough.
    • Serve with other notable vegetable side dishes like my Roasted Fennel, Honey Roasted Delicata Squash, or this Mediterranean Vegetable Medley.

    Browse all Mediterranean recipes. 

    Visit Our Shop.

    Roasted red onions on a platter with a serving spoon.

    Print

    Balsamic Roasted Onions

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    This side dish spotlights the humble onion, is easy to make, and tastes absolutely delicious. The silky, sweet and savory caramelized wedges will win you over from the first bite.
    Course Side, Side Dish, Sides
    Cuisine Italian/Mediterranean
    Diet Gluten Free, Vegan, Vegetarian
    Prep Time 15 minutes minutes
    Cook Time 35 minutes minutes
    Total Time 40 minutes minutes
    Servings 6
    Calories 170.9kcal
    Author Domenica Marchetti

    Ingredients

    • 6 medium red onions (1 1/2 pounds)
    • 2 tablespoons extra virgin olive oil
    • Fine salt
    • Freshly ground black pepper

    For the Balsamic Vinaigrette

    • 1 tablespoon apple cider vinegar or white wine vinegar
    • 1 tablespoon balsamic vinegar
    • 1/4 teaspoon salt
    • 1/8 teaspoon freshly ground black pepper
    • 1/2 teaspoon finely chopped fresh thyme leaves
    • 1/4 cup extra virgin olive oil

    Instructions

    • Get ready. Heat the oven to 400° F. Line a rimmed baking sheet with foil.
    • Prep the onions. Trim the ends off the onions, peel and cut them into quarters. Arrange on the prepared baking sheet and drizzle with 2 tablespoons extra virgin olive oil. Use your fingers to coat them and season with a pinch of salt and freshly ground black pepper. Roast for 15 minutes.
    • Make the vinaigrette. Meanwhile, in a small bowl, combine apple cider vinegar, balsamic vinegar, salt, pepper, and thyme. Slowly whisk in the olive oil, until the vinaigrette is emulsified.
    • Baste the onions. Remove the pan from the oven and brush the onions with about half the vinaigrette, turning them to make sure all sides are coated. Return the onions to the oven and roast until the wedges are nicely caramelized and slightly blackened in spots, another 15 to 20 minutes.
    • Finish and serve. Gently transfer the onions into a bowl. Don’t worry if they fall apart a little. Drizzle the remaining vinaigrette over them and toss gently with a spoon. Taste and adjust the seasoning with more salt or pepper if needed. Let the onions marinate for about 15 minutes before serving.

    Notes

    • Visit our shop to browse quality Mediterranean ingredients, including olive oils, honey, jams, and spices.

    Nutrition

    Calories: 170.9kcal | Carbohydrates: 10.8g | Protein: 1.2g | Fat: 14.1g | Saturated Fat: 2g | Polyunsaturated Fat: 1.5g | Monounsaturated Fat: 10.2g | Sodium: 102.3mg | Potassium: 167.1mg | Fiber: 1.9g | Sugar: 5.1g | Vitamin A: 10.3IU | Vitamin C: 8.4mg | Calcium: 27.3mg | Iron: 0.4mg

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    The Mediterranean Diet Starter Kit

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