Sweet Red Pepper Relish

12 large red bell peppers, cored, seeded, and moderately coarsely chopped (about 4½ pounds)
12 very small yellow onions, moderately coarsely chopped (about 2 pounds)
12 small Golden Delicious apples, cored, peeled, and moderately coarsely chopped (about 4 pounds)
3 quarts boiling water (about)
2½ cups cider vinegar
2½ cups cold water
2½ cups sugar
4 teaspoons pickling salt

To avoid spilling or dribbling relish down the sides of the jars as you fill them, use a wide-mouth canning funnel.

Place the peppers, onions, and apples in a very large nonreactive kettle, add just enough of the boiling water to cover them, and let stand uncovered at room temperature for 10 minutes.
Meanwhile, wash and rinse 11 one-pint preserving jars and their closures and submerge in a large kettle of boiling water.
Combine the vinegar, cold water, sugar, and salt in a medium-size nonreactive kettle and bring to a boil over moderate heat. Reduce the heat to low, stir until the sugar dissolves completely, then simmer uncovered for 5 minutes.
Drain the vegetable mixture well and return to the same kettle. Pour in the hot vinegar mixture, set over moderate heat, and bring to a full rolling boil. Set off the heat.
Lift the preserving jars from the boiling water one by one. Ladle in the hot relish, leaving ¼ inch head space at the top of the jar. Run a thin-blade spatula around the inside of the jar to free trapped air bubbles; wipe the jar rim with a clean, damp cloth, then screw on the closure. Repeat until all the jars are filled.
Process the jars for 10 minutes in a boiling water bath (212° F.). Lift from the water bath; complete the seals, if needed, by tightening the lids, then cool to room temperature.
Date and label each jar, then store on a cool, dark shelf several weeks before opening.