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    Home » Recipes » Condiments

    Sweet Onion Sauce

    Published: Jan 19, 2023 · Modified: Mar 10, 2023 · by Puja Verma

    Jump to Recipe Print Recipe

    This sweet onion sauce is quick, easy, and made with minimal ingredients. It’s just what your sandwiches, homemade subs, and salads have been needing! Try this Subway copycat for a slightly tangy, sweet, and preservative-free option when the need arises.

    A glass bottle of sweet onion sauce with lid on it.

    Why you’ll love this recipe

    • Easy: Whisk, blend, and strain — that’s all there is to it for this easy recipe.
    • Affordable: Using affordable everyday ingredients, this is a sauce you can make over and over again.
    • Versatile: Use Subway sweet onion sauce on salads, sandwiches, wraps, and more. The options are endless!
    • Customizable: Make it sugar-free, creamy, spicy, or extra herbaceous. It’s extremely easy to customize this sauce.

    What is sweet onion sauce?

    If you’ve ever tried Subway’s infamous sweet onion sauce and couldn’t get enough, I have got a surprise for you! This homemade version tastes just like the original, but it can be made in the comfort of your own home. Plus, it doesn’t contain any hard-to-pronounce additives!

    This simple dressing is made with just 6 ingredients, and it highlights a perfect balance between sweet and tangy. While a homemade sub is the most obvious choice to serve it on, this all-purpose sauce is great on all types of salads, from garden to quinoa!

    Is sweet onion sauce vegan?

    Much like the original, this sweet onion sauce is vegan-friendly since it contains no animal-derived products. If you’re more strict on how your ingredients are processed, ensure you’re using organic vegan sugar that’s not processed with bone char.

    Ingredients & Substitutions

    Sweet onion sauce ingredients laid out and grouped individually.
    • Onion: Use white or yellow onions, although I prefer white onions for their crisp, clean flavor. If you can get your hands on some, I also recommend sweet onion varieties like Vidalia and Walla Walla.
    • Water: To thin the sauce and mix with the potato starch.
    • Sugar: Adds sweetness, balancing and enhancing the natural sweetness of the onions. Use cane sugar or vegan granulated sugar.
    • White wine vinegar: I prefer the slightly sweeter, milder, and more delicate taste of white wine vinegar over regular white vinegar. It results in a well-rounded sauce rather than one overpowered by acidity.
    • Poppyseeds: Just like Subway’s sweet onion sauce, don’t forget to include poppyseeds!
    • Salt & pepper: Brings out the flavor of the sauce while adding a little kick!
    • Potato starch: To thicken the sauce. If you don’t have potato starch, cornstarch is a great substitute.

    Instructions

    A bowl of potato starch slurry.
    • Step 1: To make the slurry, whisk together the potato starch and water in a small bowl.
    Onion juice blend in an open blender cup.
    • Step 2: Roughly chop the onions and toss them into a blender with water. Mix them on high until they’re smooth (like onion juice).
    Onion pulp straining through a mesh sieve with a silicon spatula over a sauce pan.
    • Step 3: Strain the onion juice through a fine-mesh sieve into a saucepan, using a spoon to slowly push the liquid through. It mostly all goes through the mesh sieve.
    A sauce pan with onion juice and poppy seeds getting stirred with a wooden spoon.
    • Step 4: Heat the saucepan of onion juice over low-medium, then add the slurry and the remaining ingredients to thicken the sauce.
    Sweet onion sauce drizzling down in a pool of onion sauce with a metal spoon.
    • Step 5: Bring the sauce to a quick boil, then immediately turn off the heat and let it cool. This sweet onion sauce will thicken more as it continues to cool.

    How to use Subway sweet onion sauce

    Once your onion sauce is cooled and thickened, use it in some of the following ways:

    • Drizzled on sandwiches, subs, and paninis
    • Served in wraps and pitas
    • As a dip for pizza
    • Used as a salad dressing
    • Tossed with roasted vegetables

    Storage

    If you have leftover sauce, you’re in luck! It can be stored for quite a long time by following these storage instructions:

    • Fridge: As long as it’s kept in an airtight container (I prefer a mason jar), this dressing will stay fresh for up to a month in the fridge.
    • Freezer: This sauce is freezer-friendly, and the storage time can be extended up to 3 months. Just keep it in a freezer-safe container or jar.
    • Thaw: When you’re ready to use it again, thaw the sauce in the fridge overnight. Don’t forget to give it a stir in the morning, especially if it’s separated.
    A spoonful of sweet onion sauce.

    Variations

    • Sugar-free: Swap the sugar for stevia for a keto, diabetic, and sugar-free version.
    • Creamy: For a creamier version, try adding 1-2 tablespoons of my vegan Kewpie mayo.
    • Spicy: Add a slight kick with a teaspoon of Sriracha or sambal oelek.

    Top tips

    • Strain the onions: For the smoothest sweet onion sauce, blend and strain the onions into the saucepan.
    • Simmer the sauce: To bring the flavors together and thicken the sauce, don’t skip simmering it.
    • Make a slurry: To prevent the potato starch from clumping in the sauce, combine it with a small amount of water before adding it in.
    Top view of an open glass bottle with onion sauce in it.

    FAQ

    Is sweet onion sauce gluten-free?

    This sweet onion sauce is gluten-free the way it’s written in the recipe. However, if you suffer from Celiac disease, it’s best to double-check each individual ingredient.

    Did Subway discontinue its sweet onion sauce?

    Yes, Subway unfortunately discontinued its sweet onion sauce and replaced it with sweet onion teriyaki sauce. The good news is you’ll be able to make your own Subway sweet onion sauce by following this simple recipe!

    Do I have to strain the sauce? 

    No, you don’t have to strain the sauce. However, if you skip this step, it will be quite chunky in its final form. 

    Similar Recipes

    If you enjoyed this recipe, be sure to check out some more of my most popular sauces like these:

    • Southwest Salad Dressing: A creamy, spicy, and tangy sauce made in 5 minutes.
    • Vegan Caesar Dressing: Simple Caesar dressing made with plant-based ingredients. 
    • Sriracha Aioli: A rich vegan aioli with a spicy element!
    • Maple Dijon Vinaigrette: Healthy dressing made with pantry staples.
    • Caramelized Onions: If you love onions, try these sweet caramelized onions made without any sugar.
    Sweet onion sauce in a glass bottle with a lid.

    Sweet Onion Sauce

    5 from 2 votes
    Prep Time: 2 minutes mins
    Cook Time: 10 minutes mins
    Total Time: 12 minutes mins
    Serving Size: 4 people
    Author Puja Verma
    Print Recipe Pin Recipe

    DESCRIPTION

    Easy to make sweet onion sauce using basic ingredients and a few simple steps. A delicious addition to sandwiches or salads. It's perfectly balanced with sweet and tangy flavors and very similar to Subway's sweet onion sauce, but without any preservatives.

    INGREDIENTS
      

    • 1 cup onion chopped
    • ¼ cup water
    • ½ cup sugar
    • 2 teaspoon white wine vinegar
    • ½ teaspoon poppyseeds
    • ½ teaspoon salt
    • ⅛ teaspoon black pepper

    Slurry

    • 3 teaspoon potato starch or corn starch
    • ¼ cup water

    METHOD
     

    • To make the slurry: Whisk together the potato starch and ¼ cup water in a small bowl and keep aside.
    • Roughly chop the onions and toss them in the blender with water. Blend till smooth like onion juice.
    • Strain the onion juice into a mesh sieve. Use a spoon to slowly push through mostly all the pulp.
    • Heat the saucepan with onion juice over low-medium heat and add the remaining ingredients along with the slurry to thicken the sauce.
    • Bring sauce to a quick boil and then immediately turn off the heat to let the sauce cool and thicken.
      Note: Sauce will thicken more once it cools down completely.

    NOTES

    • Strain the onions: For the smoothest sweet onion sauce, blend and strain the onions into the saucepan.
    • Simmer the sauce: To bring the flavors together and thicken the sauce, don’t skip simmering it.
    • Make a slurry: To prevent the potato starch from clumping in the sauce, combine it with a small amount of water before adding it in.

    NUTRITION

    Calories: 118kcal | Carbohydrates: 30g | Protein: 1g | Fat: 0.3g | Saturated Fat: 0.04g | Polyunsaturated Fat: 0.1g | Monounsaturated Fat: 0.03g | Sodium: 296mg | Potassium: 73mg | Fiber: 1g | Sugar: 27g | Vitamin A: 1IU | Vitamin C: 3mg | Calcium: 17mg | Iron: 0.2mg
    Course: Condiments
    Cuisine: American
    Keyword: subway sweet onion sauce, sweet onion sauce
    Tried this recipe?Let us know how it was!
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    Puja from Green Heart Love

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