4 medium peaches, about 1 1/2 pounds, peeled and cut into 1/2-inch-wide slices
3/4 cup sugar
1/2 cup cider vinegar
1/4 teaspoon hot red-pepper flakes
1 small red onion, halved lengthwise and sliced crosswise 1/8 inch thick (1 cup)
3/4 teaspoon salt
Directions
Combine peaches, sugar, vinegar, and hot pepper flakes, and briskly simmer, uncovered, until liquid thickens slightly, 15 to 20 minutes. Stir in onion and salt and simmer for 5 minutes. Relish will continue to thicken as it cools.
