Chow Chow

5 cups coarsely chopped green tomatoes
5 cups coarsely chopped cabbage
1 1/2 cups finely chopped yellow onion or sweet onion
2 cups coarsely chopped bell pepper, at least 1 red for color
1/3 cup kosher salt or pickling salt
2 1/2 cups cider vinegar
1 cup light brown sugar, packed
1 tablespoon yellow mustard seeds
2 cloves garlic, finely minced
1 teaspoon celery seed
1/2 teaspoon red pepper flakes, or to taste, optional
Combine the chopped vegetables in a large nonreactive kettle or bowl. Add the salt and stir to combine thoroughly. Cover and let stand for 4 hours or refrigerate overnight. Drain the vegetables and rinse thoroughly. In a large nonreactive stockpot bring the vinegar, brown sugar, and seeds and spices to a boil. Reduce heat to medium low and continue simmering for 5 minutes. Add the drained vegetables and bring back to a boil. Reduce heat to medium low and simmer for 10 minutes. With a slotted spoon, pack the vegetables into prepared jars. Cover vegetables with the pickling liquid, leaving about 1/4-inch headspace. With a clean dampened cloth, wipe the rims of the jars. Place the flat lids on the jars then close caps with screw-on rings tightly, but do not over-tighten. Arrange the filled jars in the canner and add more water, as needed, to be at least 1 inch above the jars. Bring to a full boil. Cover and continue boiling for 10 minutes. Remove the relish to a rack to cool completely.