Sweet Onion Sauce {Subway Copycat Recipe}

Name: Sweet Onion Sauce {Subway Copycat Recipe}
Prep time: 10 min
Cook time: 5 min
Total time: 15 min
Ingredients: 1 cup granulated sugar; ½ cup + 1 tablespoon water; 6 tablespoons white vinegar; 4 ½ teaspoons red wine vinegar; 1 teaspoon finely grated onion (using a small holed grater or garlic press); 1 tablespoon dijon mustard; ¼ tsp. Sesame oil; 1 tablespoon cornstarch; 1 tablespoon dried minced onion; 2 tsp. Dry mustard powder; 1 tsp. salt; ¾ tsp. Poppy seeds; ½ tsp. Celery seed; ¼ tsp. Onion powder; ¼ tsp. Paprika (heaping); ¼ tsp. Ground black pepper (heaping); ⅛ tsp garlic powder (heaping)

Why go out to eat when you can stay at home!? This copycat recipe for Subway's Sweet Onion Sauce is CRAZY easy to make from scratch. You're going to wonder why you didn't start making this flavor-packed sauce sooner! Great for adding to your favorite homemade subs, sandwiches, salads and more!

Adding sweet onion sauce to a homemade sub.

Who else has their Subway order down to a science? ✋ I know I do! BLT on Italian Herb and Cheese, orange cheddar, with lettuce, tomato, cucumber, black olives, pickles, and just a few banana peppers. Top that baby off with some mayo and some sweet onion sauce! I can almost taste that deliciousness as I type it out.

As much as I love going out to eat, I also happen to love staying at home and making my own versions of popular restaurant favorites. This copycat recipe for Subway's Sweet Onion Sauce is an easy one, great for keeping stashed in your fridge for topping your homemade subs with. That signature tang and sweetness of Sweet Onion Sauce is what makes the Subway experience for me. So naturally, if I'm making my subs at home I want to emulate that signature flavor! If you're a fan of this tangy sauce, I'm sure you feel the exact same way!

An Easy Subway Copycat Recipe

The best thing about this recipe is that it is made with ultra simple ingredients. You probably have everything you need in your pantry right now!

In addition to the simplicity of the ingredients, it also lasts a good while in the fridge! I recommend using your Sweet Onion Sauce within 2 to 4 weeks for the best results, but it will last much longer than that. Since all of the ingredients have a long shelf life, the resulting sauce will have a long shelf life as well! As with all things, exercise caution and if in doubt, throw it out. Ensure to keep your sweet onion sauce in an airtight container in the fridge at all times.

Ingredients

Sugar: This provides the "sweet" in sweet onion sauce.
Grated onion: In order to keep the sauce smooth, you will need to use grated onion. I used a small rasp grater to grate it into a juicy paste. You can also use a garlic press, but I recommend grating it if you can. Just be careful of those fingers!
Vinegar: Everything sweet needs a little sour! Classic white vinegar is clean tasting, and perfect for this recipe.
Red wine vinegar: You will also need a bit of red wine vinegar. This adds another flavor element, and is really lovely in this recipe!
Dijon mustard: Smooth, slightly spicy Dijon mustard adds the perfect flavor kick here.
Corn starch: Acts as a thickener, giving the Sweet Onion Sauce that perfect consistency.
Sesame oil: Just a touch! You can use regular sesame oil, or toasted sesame oil.
Seasonings: You will need dried minced onion, dry mustard powder, salt, poppy seeds, celery seeds, onion powder, paprika, black pepper, and garlic powder.
Water: This prevents the sauce from being too concentrated. Don't worry, the corn starch will help thicken the mixture up so it won't be watered down at all!

How to Make Sweet Onion Sauce

To get started, all you'll need a medium sized saucepan and a whisk! This is such a simple recipe.

Add all of the ingredients to the saucepan and whisk well to combine.

Bring to a boil over medium-high heat, whisking often to prevent burning.

Reduce the heat to low and simmer until thickened, about 5 minutes.

Ensure to whisk frequently to prevent burning and help the sauce thicken evenly.

Storage

Allow to cool completely, then transfer to an airtight container and label. Store in the refrigerator and use within 4 weeks, or freeze for longer storage. If you'd like to keep it in a squeeze bottle, I recommend these squeeze bottles, which have an airtight cap.

Substitutions

Keto, Sugar Free, and Diabetic Friendly: Substitute the sugar for a low carb sweetener that measures cup for cup with sugar. I recommend Swerve or Lakanto.

Gluten Free: Verify the individual ingredients (like dijon mustard, red wine vinegar, and sesame oil) are free from gluten or contaminants. Otherwise, this recipe is gluten free as written.

Dairy Free: This recipe is dairy free as written.

FAQ

Is Sweet Onion Sauce keto friendly?

While the restaurant version of Sweet Onion Sauce is made with heavy amounts of sugar, if you make it at home with sweetener, you can have a yummy version of Sweet Onion Sauce as a part of your keto lifestyle.

How long will homemade sauce last?

Depending on the ingredients, homemade sauces will last anywhere from a few days, to a few months. A vinegar and spice based sauce (like sweet onion sauce) will have the highest quality and last anywhere from 2-4 weeks. An egg based sauce may only last a few days.

Sweet onion sauce being squeezed onto a homemade sub.

Serve With:

Homemade subs
Homemade sandwiches
Mixed with teriyaki sauce
Salads
Panini
Pizza

More Copycat Subway Recipes:

Italian Herb and Cheese Bread - Maritime Glutton
Copycat Subway Meatball Marinara Sandwich - The Big Man's World
Best Subway Tuna Salad Sandwiches - Kitchen Divas
White Chocolate Macadamia Nut Cookies - The Big Man's World

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