Prepare a boiling water bath canner, 9 half pint jars, new lids, and clean rings.

Cut peaches in half, remove pits, and peel. Cut halves into four wedges and dice each wedge into 3-4 pieces.

Place diced peaches in a low, wide pan and add sugar, apple cider vinegar, mustard seeds, red chili flakes, and cayenne pepper.

Place the pot over high heat and bring to a boil. Cook for 5 to 6 minutes at a rapid boil, until the peaches release their juice and the syrup thickens slightly.

Using a slotted spoon, portion the peaches out into prepared jars and top each off with syrup, leaving 1/2 inch headspace. Tap jars to remove air bubbles and add more syrup if needed.

You may not have as many as 9 half pints, but it's always nice to have more prepared rather than not enough.

Once jars are full, wipe rims, apply lids and rings, and process in a boiling water bath canner for 15 minutes.

When time is up, slide canning pot off the hot burner and remove lid. Let jars cool slowly in the canning pot for at least ten minutes before removing the jars from the pot.

Place the hot jars on a folded kitchen towel and let them cool.

Once jars are cool enough to handle, test seals by pressing down on the lids. If they are firm and without wiggle, the jars are sealed.