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!
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.
- 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.
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.
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.
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.
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.
- Homemade subs
- Homemade sandwiches
- Mixed with teriyaki sauce
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
- 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
- Whisk all of the ingredients together in a small saucepan.
- 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.
- 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.
Use a rasp grater to grate the onion. Alternatively, you can use a garlic press to press the onion.
For Low Carb/Keto/Diabetic:
Use 1 cup of sweetener that measures cup for cup with sugar instead of the white granulated sugar in this recipe.
If you purchase a squeeze bottle for your sweet onion sauce, be sure to purchase one for a large enough opening for the larger pieces of dried minced onion to get through. You can also cut off a portion of the tip to make the opening larger.
Keep your sweet onion sauce in the fridge in an airtight container for up to 4 weeks.
Adapted from this recipe from Food.com.
Amount Per Serving: Calories: 89Total Fat: 0gSaturated Fat: 0gTrans Fat: 0gUnsaturated Fat: 0gCholesterol: 0mgSodium: 274mgCarbohydrates: 21gFiber: 0gSugar: 20gProtein: 0g
Nutritional information is an estimate only.
Please note that some of my blog posts here at Dash for Dinner may contain affiliate links. If you make a purchase through these links, I will get a small commission at no additional cost to you. Please see my Disclaimer for more information.