Subway-Style Sweet Onion Sauce

Featured in Flavorful Sauces & Marinades.

Homemade version of Subway's sweet onion sauce. Takes 15 minutes to make, stores for a week in the fridge.
Casey
Updated on Wed, 22 Jan 2025 18:00:54 GMT
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When Subway discontinued their sweet onion sauce, I went into full-blown recipe detective mode. After all, this wasn't just any sauce - it was the one that made every sandwich special. Through countless kitchen experiments (and many willing taste-testers), I've finally cracked the code to recreating that perfect balance of sweet, tangy, and savory flavors.

After making this sauce weekly for months now, I can honestly say it's become a staple in my kitchen. My family actually prefers it to the original - they say it tastes brighter and more complex.

Essential Ingredients

  • Sweet Onion - The star of the show. I've tried every variety, but sweet onions give that perfect mild flavor
  • Two Vinegars - The combination of red and white vinegar creates layers of tang
  • Sesame Oil - Just a touch gives that mysterious depth the original has
  • Fresh Spices - Don't use that paprika that's been sitting in your cabinet since last year
  • Cornstarch - The secret to that perfect sauce consistency
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The Secret to Perfect Sweet Onion Sauce

1.
Let's talk about grating that onion first. I discovered through many teary-eyed attempts that using a microplane gives you the perfect consistency. If you're using a regular grater, use the smallest holes - we want the onion almost liquified
2.
Here's my game-changing discovery - warm your vinegars slightly before mixing with the sugar. It helps everything dissolve perfectly and brings out the flavors of the spices
3.
When you're cooking the sauce, patience is key. Let it come to a gentle simmer, not a rolling boil. I once rushed it and ended up with a sauce that was too thick

Kitchen Secrets I've Found

* Use fresher poppy seeds - old ones can make your sauce taste bitter
* Stir your cornstarch with cold water first to prevent lumps
* Let the sauce cool completely before bottling - it thickens as it cools

Common Problems Solved

After making this sauce countless times, here's what I've learned:
* Too thick? Add a splash of water while it's still warm
* Too thin? Mix a little more cornstarch with cold water and stir it in
* Not enough tang? Add vinegar a teaspoon at a time until it's perfect

Creative Ways to Use Your Sauce

After making this sauce almost weekly, I've discovered it's way more versatile than just sandwich spreading. Here's what works amazingly well:

Beyond Sandwiches

* Brush it on grilled chicken during the last few minutes of cooking
* Toss it with warm roasted vegetables - especially sweet potatoes
* Mix it into your tuna or chicken salad for extra zing
* Use it as a unique pizza drizzle

Protein Perfect

* Brush it on salmon during the last few minutes of baking - it caramelizes beautifully
* Use it as a marinade for grilled shrimp - 30 minutes is perfect
* Drizzle over sliced steak for an unexpected twist
* Mix into egg salad for the best sandwich filling ever

Salad Stars

* Toss with warm roasted vegetables right out of the oven
* Use as a unique pasta salad dressing - add cherry tomatoes and cucumber
* Mix with quinoa and roasted vegetables for a grain bowl
* Create an Asian-inspired slaw with shredded cabbage and carrots

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Easy Homemade Subway Sweet Onion Sauce | cookingwithcasey.com

Snack Attack

* Dipping sauce for crispy onion rings
* Drizzle over loaded baked potatoes
* Toss with air-fried vegetables
* Mix with cream cheese for a unique bagel spread

Party Perfect

* Drizzle over a platter of grilled vegetables
* Use as a dip for vegetable spring rolls
* Brush on grilled corn on the cob
* Mix into burger meat before grilling for extra flavor

Unexpected Winners

* Stir into scrambled eggs at the end of cooking
* Brush on roasting brussels sprouts
* Use as a pizza finishing sauce
* Mix into mashed potatoes for extra zip

Storage Secrets

Through trial and error, I've found these storage tricks work best:
* Use a clean squeeze bottle - makes it easy to control portions
* Keep it in the coldest part of your fridge, not the door
* If it thickens too much after chilling, let it sit out for 5 minutes

Perfect Pairings

My family's favorite combinations:
* Drizzled over a turkey and avocado wrap
* Mixed into coleslaw for a unique twist
* As a dipping sauce for sweet potato fries
* Tossed with fresh cucumber slices

Final Thoughts

This sauce has become more than just a Subway copycat in our house - it's evolved into our own special condiment. Every time I make it, I think of new ways to use it. Just last week, I discovered it makes an amazing marinade for grilled vegetables!

Remember, the beauty of making your own sauce is that you can adjust it to your taste. Want it sweeter? Add more sugar. Love tang? Up the vinegar. It's all about making it perfect for your palate.

Homemade Sweet Onion Sauce

Recreate Subway's famous sweet onion sauce with this easy copycat recipe. Perfect blend of sweet and tangy flavors.

Prep Time
5 Minutes
Cook Time
10 Minutes
Total Time
15 Minutes
By: Casey


Difficulty: Easy

Cuisine: American

Yield: 8 Servings (2 cups)

Dietary: Vegan, Vegetarian, Gluten-Free, Dairy-Free

Ingredients

→ Main Ingredients

01 1 Cup Sugar
02 1/2 Cup Water
03 6 Tablespoons White Vinegar
04 1 1/2 Tablespoons Red Wine Vinegar
05 1/2 Tablespoon Onion, freshly grated
06 1 Tablespoon Cornstarch
07 2 Teaspoons Dijon Mustard
08 2 Teaspoons Mustard Powder

→ Seasonings

09 1 Teaspoon Poppy Seeds
10 1/2 Teaspoon Sesame Oil
11 1/2 Teaspoon Onion Powder
12 1/2 Teaspoon Salt
13 1/4 Teaspoon Garlic Powder
14 1/4 Teaspoon Celery Seed
15 1/4 Teaspoon Paprika
16 1/4 Teaspoon Black Pepper

Instructions

Step 01

Add all ingredients to a sauce pan.

Step 02

Bring to a boil while whisking constantly. Let boil for 5 minutes, then reduce heat to simmer for another 5 minutes, whisking continuously.

Step 03

Remove from heat and allow to cool. Store in an airtight container in the refrigerator for up to 1 week.

Notes

  1. Can be customized with less sugar or alternative sweeteners
  2. Works great as salad dressing or marinade
  3. Sauce will thicken as it cools

Tools You'll Need

  • Saucepan
  • Whisk
  • Measuring cups and spoons
  • Microplane or grater

Allergy Information

Please check ingredients for potential allergens and consult a health professional if in doubt.
  • Sesame (contains sesame oil)
  • Mustard (contains Dijon and mustard powder)

Nutrition Facts (Per Serving)

It is important to consider this information as approximate and not to use it as definitive health advice.
  • Calories: ~
  • Total Fat: ~
  • Total Carbohydrate: ~
  • Protein: ~