Wash peppers and cut in large chunks; you’ll have about 6 pounds of chunks. Finely chop about 1/2 to 2/3 of the peppers. Grind or finely chop the remaining peppers using a food grinder or food processor. Coarsely chop about half of the onions and add the remaining onions to the grinder or food processor. Combine in a large bowl with the salt; toss to mix thoroughly. Cover with ice and let stand for 3 hours.Drain peppers, squeezing to get as much moisture out as possible. In a large nonreactive kettle, combine the vinegars, sugar, mustard seeds, and paprika, if using. Add the well drained pepper mixture and bring to a boil. Reduce heat to medium low and simmer, uncovered, for 50 to 60 minutes, until thickened. Stir occasionally.Meanwhile, fill a boiling water bath canner about half full. Add clean canning jars to the water and bring to a boil. Reduce heat to low and keep jars warm.

In a saucepan, bring water to a simmer, turn to low and add the flat lids. Keep the lids in the hot water until ready to use.

When the pepper mixture is finished cooking, ladle into the hot drained jars. With a damp clean cloth, wipe the rims of the jars. Using tongs, lift lids from the water and let excess drip off of them; place on the clean jar rims. Screw on the jar rings firmly. Lift jars into the canner. Bring to a boil, cover, and boil gently for 10 minutes.

Makes about 5 to 6 pints.