This homemade pickle relish is the perfect sweet and tangy topping for veggie burgers, hot dogs, and more! It will keep in the fridge for up to 2 weeks.
In a small pot, combine the cucumber, bell pepper, onion, and ¼ cup of the apple cider vinegar. Bring to a simmer and cook for 10 minutes, stirring occasionally. Drain and discard any excess liquid.
Return the veggies to the pot and add the remaining ¼ cup apple cider vinegar, the sugar, mustard seeds, salt, red pepper flakes, and celery seed. Simmer for 5 minutes.
Remove the relish from the heat and let cool to room temperature. Chill until ready to use.