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5.0 from 63 votes

Subway Sweet Onion Sauce Recipe

Subway copycat sweet onion sauce recipe at home from scratch within 15 minutes. An easy, vegan, gluten-free, oil-free, recipe.

Prep Time
5 mins
Cook Time
5 mins
Total Time
15 mins
Servings: 1 cup
Course: Side Dish , Condiments
Cuisine: International

Ingredients

  • 1 medium-size onion
  • 2 garlic cloves
  • ¾ cup water plus ¼ cup water
  • ⅓ cup granulated sugar
  • 1 teaspoon balsamic vinegar
  • 1 teaspoon white vinegar
  • ¼ teaspoon nigella seeds/kalonji
  • ¼ teaspoon black pepper, freshly ground or to taste
  • ¼ teaspoon salt or to taste
  • 2 teaspoon cornflour/cornstarch
  • ½ teaspoon lemon juice, fresh

Instructions

    Cup of Yum
  1. Peel the onion and garlic, roughly chop them, and blend until look smooth. Squeeze the juice using a muslin cloth and transfer to a pan or pot.
  2. Heat the pan. Add in water, sugar, salt, white vinegar, balsamic vinegar, black pepper, and nigella seeds. Bring the mixture to a boil until sugar dissolves.
  3. Whisk ¼ cup water and cornflour together in a bowl, and make a slurry.
  4. Add the cornflour slurry and stir continuously over medium flame until the sauce thickens and looks glossier.
  5. Remove from heat and add lemon juice. Stir to mix and allow the sauce to come to room temperature.
  6. Store in an airtight container in the refrigerator and use when needed.

Notes

  • Be sure to give the sauce a taste test to avoid over-seasoning. 
  • Be sure to give the sauce a taste test to avoid over-seasoning. 
  • Ingredient notes: 
  • Onion: any sweet variety; Some popular sweet onion varieties include Walla walla, Texas sweets, Maui, and Vidalia. White or yellow onion will work as well.
  • : any sweet variety; Some popular sweet onion varieties include Walla walla, Texas sweets, Maui, and Vidalia. White or yellow onion will work as well.
  • Garlic: just a touch of fresh garlic to enhance the flavor. If fresh garlic is not available, you can use garlic powder instead. 
  • : just a touch of fresh garlic to enhance the flavor. If fresh garlic is not available, you can use garlic powder instead. 
  • Vinegar: plain white distilled vinegar and balsamic vinegar.
  • : plain white distilled vinegar and balsamic vinegar.
  • Granulated sugar: you can also use brown sugar. 
  • : you can also use brown sugar. 
  • Cornflour: cornflour or cornstarch to thicken the sauce. Arrowroot flour, tapioca flour/starch, or potato starch also work fine;
  • : cornflour or cornstarch to thicken the sauce. Arrowroot flour, tapioca flour/starch, or potato starch also work fine;
  • Black pepper powder: I recommend using freshly ground black pepper; 
  • : I recommend using freshly ground black pepper; 
  • Nigella seed(also called kalonji): available in Asian grocery stores. It tastes like oregano and onion mix. It adds a hint of extra flavor. I like the flavor, but you can choose to skip it; 
  • (also called kalonji): available in Asian grocery stores. It tastes like oregano and onion mix. It adds a hint of extra flavor. I like the flavor, but you can choose to skip it; 
  • Lemon juice: fresh;
  • : fresh;
  • Salt: I use regular table salt. 
  • : I use regular table salt. 
  • Water: cold filtered water;
  • : cold filtered water;