Prepare a water bath canner, jars, and 2-part lids for canning.

Remove the stem from the jalapeño peppers, gently knocking out any loose seeds.

Using a sharp knife, thinly slice the peppers into 1/8- to 1/4-inch rounds.

In a large pot, stir together the sugar, vinegar, garlic powder, turmeric, celery seeds, and cayenne pepper.

Bring the ingredients to a boil over medium-high heat and stir until the sugar has dissolved completely.

When the liquid is boiling, lower the heat and simmer for 5 minutes.

Add the jalapeño slices and simmer for another 5 minutes (make sure to have a window open or other source of ventilation during this step).

Lay out the jars and lids on a cutting board and, using a funnel and slotted spoon, fill the jars with the jalapeños. Be sure to leave 1-inch of headspace between the peppers and the underside of the lid.

Simmer the syrup for a further 5 minutes, before ladling into the jars.

Remove air bubbles and add more liquid if needed to ensure 1 inch of headspace.

Apply lids, screwing the outer band until fingertip tight .

Place the jars in the hot water canner, bring to a boil, and process for 10 minutes (if using half-pint jars) and 15 minutes (if using pint jars).

Once the timer has gone off, wait 5 minutes and then remove the jars.

Place the jars on a clean surface and allow the contents to come to room temperature (around 12 hours).

Check the seals on each jar, storing any unsealed jars in the fridge.

Store cowboy candy in a cool, dark place until ready to use.