Prepare peppers by cutting into rings and removing seeds and membranes if desired. Chop onions and garlic and set aside with peppers.

In a 4-quart saucepan, bring the vinegar, sweetener, mustard seed, turmeric, and celery seed to a boil. Add in the peppers, onions, and garlic and let simmer for 5-7 minutes or just until the peppers have softened slightly. The peppers should be darker.

Use a slotted spoon to remove the peppers, onion, and garlic from the brine and place in a glass jar.

Boil the remaining brine for 10-15 minutes or until it has reduced into a thick syrup. Remove from heat and ladle the thickened syrup over the pepper mixture.

Cover with an airtight lid and let cool to room temperature before refrigerating.

Let sit for at least a week before serving. The flavor will intensify over time.

The peppers can be refrigerated for up to two to three months.