Canning Sweet Onion Relish | Requested Recipe!

Today’s recipe is one that’s been requested over and over—and for good reason.

It’s sweet, tangy, versatile, and once you try it, you’ll wonder how your pantry ever got by without it.

We’re talking about our Sweet Onion Relish—a tried-and-true favorite in our home.

We made it for the first time two years ago, and it quickly earned a permanent place on our shelves. So much so that we went through all 24 pints in less than a year.

Let’s dive in!

Why We Love This Relish

• It’s sweet, but not too sweet
• Adds a burst of flavor to burgers, hot dogs, sandwiches, wraps, and even roasted veggies
• Canning-safe and shelf-stable for a full year or more
• Uses up bulk onions from your garden, farmer’s market, or grocery store

And best of all, it’s easy to scale!

The full recipe below makes 24 pints. Just cut it in half if you’re working with a smaller batch.

Ingredients (for 24 pints)

• 25 lbs of onions (weigh with skins on)
• ¾ cup salt (for soaking the onions—not flavoring)
• 10 cups apple cider vinegar (do NOT substitute white vinegar—it affects the flavor!)
• 5 cups sugar
• 5 tablespoons mustard seed
• 5 teaspoons dry mustard powder

⚠️ Important: Don’t mix up the mustard measurements—one is in tablespoons, one in teaspoons. Don’t ask how we know….

Step-by-Step Instructions

1. Chop the Onions

• Peel and roughly chop onions (a food processor is your friend here!)
• Aim for a fine mince—think small relish-size pieces
• You’ll lose about a pound or two during peeling and trimming, which is just right
  
  Eye-Watering Tip: Stick a piece of bread in your mouth while chopping. It sounds odd, but it helps! So does keeping a bowl of water nearby.

2. Salt Soak (Draw Out Moisture)

• Place chopped onions in a large stock pot
• Mix in ¾ cup of salt
• Let sit for at least 45 minutes (longer is fine)
• Cover with a clean towel if leaving on the counter, or refrigerate if soaking longer

3. Drain & Rinse

• After soaking, drain off the onion liquid
• Give them a good rinse to remove excess salt
• Set aside while you make the brine

4. Make the Brine

In a large stock pot, combine:

• 10 cups apple cider vinegar
• 5 cups sugar
• 5 tbsp mustard seed
• 5 tsp dry mustard powder

Whisk and bring to a full boil.

5. Add Onions to the Brine

• Carefully stir in the onions (we use a 1-cup scoop to avoid splash burns)
• Return mixture to a boil, then reduce to a gentle simmer for 20–30 minutes

The mixture will turn a pretty pink hue—totally normal!

6. Can It Up!

While simmering:

• Prep your water bath canner (half full of water with rack inserted)
• Heat jars in warm water
• Ladle relish into hot jars, leaving ½-inch headspace
• Debubble, wipe rims, and place new lids and rings (fingertip tight)
• Process in boiling water bath for 15 minutes. Check your elevation and adjust time if needed.

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7. Cool & Store

• After processing, turn off heat
• Let jars sit in canner 5 minutes with lid off
• Remove jars and let cool undisturbed for 12–24 hours
• Label with date and store in a cool, dark place

How We Use Onion Relish

• Topped on burgers or brats
• Mixed into egg salad or deviled eggs
• Added to charcuterie boards for a tangy punch
• Stirred into pasta salad for a sweet-savory twist
• Served alongside grilled meats or roasted veggies

It’s sweet, it’s zesty, and it brings a little extra “mmm!” to just about everything.

This sweet onion relish is a small-batch hero and a pantry MVP. It’s not only delicious but makes the most of simple ingredients—and stretches your food dollars a long way!