Wearing gloves, slice the jalapeños into 1/4-inch thick rounds. Set aside.

In a large, non-reactive pot, combine the vinegar, sugar, turmeric, celery seed, granulated garlic, and cayenne pepper (if using).

Bring the mixture to a boil over medium-high heat, stirring until the sugar is completely dissolved. Reduce heat to a simmer.

Add the sliced jalapeños to the simmering syrup. Return the mixture to a simmer.

Simmer for exactly 5 minutes. The jalapeños will turn a slightly duller green.

Using a slotted spoon, remove the jalapeños from the syrup and distribute them evenly into the prepared canning jars (or a large, clean bowl if not canning).

Bring the remaining syrup back to a rolling boil.

Boil the syrup for 5 minutes to reduce and thicken it slightly.

Carefully pour the hot syrup over the jalapeños in the jars, leaving 1/2 inch headspace.

If canning, wipe the rims, place the lids and rings, and process in a boiling water bath for 10 minutes. If not canning, let cool completely, then seal and refrigerate. The flavor will improve after 2 weeks.