How to Make It
In a very large bowl, toss the bell peppers, tomatoes, onions and cabbage with the salt; cover and refrigerate overnight.
Drain the vegetables, discarding the liquid. In a large, heavy pot, bring the sugar, vinegar and water to a boil. Add the mustard seeds, dry mustard, crushed red pepper, celery seeds, ginger and turmeric and stir well. Add the drained vegetables and bring to a boil. Simmer over moderate heat, stirring occasionally, until the relish is thick and saucy, about 1 hour. Pack the chowchow into 6 hot 1-quart canning jars, leaving 1/2 inch of space at the top, and close with the lids and rings.
To process, simmer the jars at 180° for 30 minutes and monitor the water temperature with a thermometer. Store the jars in a cool, dark place for at least 2 weeks before serving, to allow the flavors to meld; store unopened for up to 1 year. Refrigerate after opening.
Plus: Canning 101 for information on basic canning equipment and techniques.