Recipe: Fermented Onion Pepper Relish

A perfect condiment for summer grill outs (or really any occasion), this fermented onion pepper relish adds some kick to burgers, sandwiches and much more.

by Stephanie Thurow
PHOTO: Stephanie Thurow

This fermented onion pepper relish is a welcome condiment at any grill out. It’s great on sandwiches and burgers, mixed into tuna, stirred into pasta salad, or topped over tacos. 

Yield: 1 wide mouth quart jar 


  • 3 cups onions, thinly sliced (I prefer yellow onions, but you can use white or red) 
  • 2 cups red bell peppers, thinly sliced 
  • 1/4 cup jalapeño peppers, thinly sliced 
  • 1/2 tsp. celery seed 
  • 2 cloves fresh garlic, minced 
  • 2 tsp. kosher salt 

Read more: Check out this recipe for simple fermented table radishes!


Clean and chop ingredients, and mix them together with celery seeds. Sprinkle salt over the mixture and stir well 

Pack clean quart canning jar with prepared ingredients, leaving 1 1/2 inches of headspace (room from the top of the veggie mixture to the rim of the jar. A brine will naturally be created as the salt pulls liquid from the produce.

Use the back of a spoon or your clean fist to pack the ingredients tightly into the jar. If you have a small fermentation jar weight, add it to the jar to hold down the produce under the brine.

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Wipe off the rim of the jar with a clean dampened towel. Add the Mason jar canning lid and tightly screw on the ring. 

fermented onion pepper relish
Stephanie Thurow


This relish recipe is a four-to-five-day ferment. Ferment at room temperature, ideally between 60-75 degrees F (15-23 degrees C) and keep out of direct sunlight.  

Check on the ferment daily to make sure the brine is covering all the produce. If the produce has floated above the brine level, use a clean utensil to push it back below the brine or scoop it out and discard.  

Burp the jar daily. Unscrew the lid briefly and tighten it back on to allow any built-up gas to release (and avoid possible jar breakage or the ferment from overflowing). 

Once fermentation is complete, transfer the jar into the refrigerator, with the brine and all. 

Fermentation does not stop once the ferment is transferred to the refrigerator, however it does slow the process way down. The taste and texture will continue to change, therefore this ferment is best enjoyed within six months. 

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Side Notes 

If you do not have a glass jar weight, you can improvise by using an easily removable small food-grade glass dish that fits inside the jar. Or, if you have a smaller glass canning jar that can fit into the mouth of the jar you are fermenting with, you can use that to keep the produce pushed under the brine. 

If you are unsure if your water is safe for fermentation, you can boil it and allow it to cool to room temperature before stirring in the salt to make your brine. 

You may substitute fine sea salt instead of coarse kosher salt if you prefer. The measurement will remain the same for this fermented onion pepper relish recipe. 

This recipe has been adapted from Can It & Ferment It (expanded 2020 edition) with permission from Skyhorse Publishing, Inc. 

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