Put on kitchen gloves. Wash jalapenos, remove stems, and slice into uniform 1/4 inch rings.

In a large heavy-bottomed pot, combine apple cider vinegar, granulated sugar, turmeric, celery seed, garlic powder, and cayenne pepper. Stir over medium heat until sugar dissolves, about 5 minutes.

Increase heat to high and bring the mixture to a full rolling boil. Boil without stirring for 5 minutes.

Add sliced jalapenos to the boiling syrup, stir gently to coat, reduce heat to medium, and simmer for exactly 4 minutes.

Using a slotted spoon, transfer jalapenos to a heat-proof bowl. Return syrup to a boil and cook for 6 minutes until slightly thickened.

Pack hot jalapeno rings tightly into sterilized half-pint jars, leaving 1/4 inch headspace.

Ladle hot syrup over the peppers, covering them completely while maintaining 1/4 inch headspace. Remove air bubbles and wipe jar rims clean.

Apply lids and bands until fingertip tight. Process jars in a boiling water bath canner for 10 minutes, adjusting for altitude if necessary.

Remove jars carefully and let cool undisturbed for 12–24 hours. Check seals; refrigerate any unsealed jars. Allow sealed jars to rest for at least 2 weeks before opening for best flavor.