How to Make Subway Copycat Sweet Onion Sauce
If you love sandwiches as much as I do, then learning how to make this Subway Copycat Sweet Onion Sauce will elevate your sandwich game!
Ingredients
- 1 small sweet onion thinly sliced
- 1 tsp neutral oil like grapeseed or canola
- 1/4 tsp salt for caramelizing onions
- 1/4 cup water for blending onions
- 1/2 cup granulated sugar
- 3 tbsp white vinegar
- 1 tbsp red wine vinegar for depth
- 1 tsp Dijon mustard adds tang and body
- 1/4 tsp sesame oil a little goes a long way!
- 1 tbsp cornstarch or potato starch
- 1 tsp onion powder
- ¼ tsp garlic powder
- ½ tsp salt for seasoning the sauce
- ¼ tsp celery seed
- ¼ tsp paprika
- ⅛ tsp ground black pepper
- ½ tsp poppy seeds optional, adds a bit of texture and visual
Instructions
- In a small nonstick skillet over medium heat, add oil, sliced onion, and ¼ tsp salt. Cook for about 10–12 minutes, stirring often, until deeply golden and soft. Reduce heat as needed to prevent burning.1 small sweet onion, 1 tsp neutral oil, 1/4 tsp salt
- Transfer caramelized onions to a blender with ¼ cup water. Blend until very smooth. Strain through a fine mesh sieve to extract onion “juice,” discarding any remaining pulp.1/4 cup water
- Pour the onion juice into a saucepan. Add sugar, both vinegars, Dijon mustard, sesame oil, and all the spices. Whisk to combine.1/2 cup granulated sugar, 3 tbsp white vinegar, 1 tbsp red wine vinegar, 1 tsp Dijon mustard, 1/4 tsp sesame oil, 1 tsp onion powder, ¼ tsp garlic powder, ½ tsp salt, ¼ tsp celery seed, ¼ tsp paprika, ⅛ tsp ground black pepper
- In a small bowl, mix cornstarch with 1 tablespoon of water to make a slurry. Add it to the saucepan.1 tbsp cornstarch
- Heat sauce over medium heat. Bring to a gentle boil, then lower heat and simmer for 2–3 minutes, whisking constantly, until thickened and glossy.
- Remove from heat and let cool completely. Mix in the poppy seeds, then transfer to a jar or squeeze bottle and refrigerate. Sauce will thicken slightly more as it cools. Keeps for up to 4 weeks in the fridge.½ tsp poppy seeds
Tried this recipe?Let us know how it was!