Recipe: 3-Ingredient Maple-Mustard Onion Sauce

Kelli Foster
Kelli FosterCulinary Producer at The Kitchn
I'm a recipe developer, food writer, stylist, and video producer (and The Kitchn's Dinner Therapist), with more than 10 years professional experience. Since graduating from The French Culinary Institute, I've authored 3 cookbooks: Buddha Bowls, Plant-Based Buddha Bowls, and The Probiotic Kitchen.
updated Jan 29, 2020
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Credit: Joe Lingeman
This 3-ingredient sauce is just the right balance of smoky, sweet, and tangy.

Makesabout 1 cup

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(Image credit: Joe Lingeman)

If you ask me, onions spend far too much time in a supporting role, so we’re changing that with a simple sauce that packs big, bold flavor. It comes together with three basic ingredients (salt, pepper, and oil are freebies) to create a flavor-packed sauce that is just the right balance of smoky, sweet, and tangy.

How to Use This Sauce

This sauce is incredibly versatile and pairs well with just about everything in your meal plan, whether you spoon it over a grain bowl, spread it on a sandwich, or use it as a marinade or topping for sheet pan tofu. The sweetness of the roasted onion and charred, smoky undertones make it a natural pairing for everything you pull off the grill. It also seamlessly blends into your regular salad dressing.

Or you could grab your favorite soft cheese, a sleeve of crackers, this sauce, and call it dinner. We won’t tell!

Maple-Mustard Onion Sauce

This 3-ingredient sauce is just the right balance of smoky, sweet, and tangy.

Makes about 1 cup

Nutritional Info

Ingredients

  • 1

    medium Vidalia or sweet onion, unpeeled

  • 1 tablespoon

    olive oil

  • 1 1/2 tablespoons

    maple syrup

  • 2 teaspoon

    whole-grain Dijon mustard

  • 1/2 teaspoon

    kosher salt

  • 1/4 teaspoon

    freshly ground black pepper

Instructions

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  1. Arrange a rack in the middle of the oven and heat to 400°F. Place the onion in a large ramekin or small baking dish and drizzle with oil. Roast until the onion is dark on the outside and soft on the inside, 40 to 45 minutes. Cool completely.

  2. Peel and trim the onion. Place in the bowl of a food processor fitted with the blade attachment or a blender. Process until the onion is puréed with a smooth texture, 30 to 45 seconds. Add the maple syrup, mustard, salt, and pepper. Process until the sauce is well-combined, about 30 seconds. Serve immediately or store in a covered container in the refrigerator until ready to serve.

Recipe Notes

  • Make ahead: The onion can be roasted up to 1 day in advance and stored in a covered container in the refrigerator. The sauce can be made up to 1 day in advance and stored in a covered container in the refrigerator.
  • Storage: Leftover sauce can be stored in a covered container in the refrigerator for up to 3 days.