Here's the perfect solution for early-summer tomato cravings (or for those end-of-season fruits that don't ripen before the frost). For prettiest results, use a variety of colorful bell peppers: orange, yellow, purple, red, and green. If you'd like a little heat, add a jalapeno or two.
Note: If you're pressed for time, you can pulse the vegetables in a food processor until they're chopped into ¼-inch pieces. Dicing the vegetables by hand takes more time, but it makes the relish look extra pretty.
Finely dice (see Note) the tomatoes, onions, peppers, and jalapenos (if using).
Transfer the vegetables to a large bowl, stir in the pickling salt, and let stand for 1 hour. Drain and discard liquid, then add the sugar, pickling spices, and vinegar. Transfer mixture to a 4-quart pot and set it over high heat; bring to a boil. Lower heat to low and gently simmer for 1 hour.
Pack the relish into hot, fully sterilized pint jars, leaving a quarter-inch of head space at the top. Remove any air bubbles by tapping the jars lightly; wipe jar rims with a clean towel. Cover at once with metal lids, and screw on bands. Seal and process for 5 minutes in a boiling-water bath. Cool and store in a cool, dry place.