2 red onions (1 pound total), cut into 1/4-inch dice (about 3 cups)
2 red bell peppers, seeded, cut into 1/4-inch dice (about 2 1/2 cups)
1/4 cup plus 1 1/2 teaspoons coarse kosher salt
2 cups distilled white vinegar
1 1/2 cups (packed) golden brown sugar
2 garlic cloves, minced
1 teaspoon whole coriander seeds
3/4 teaspoon whole aniseed
Combine tomatoes, onions, peppers, and 1/4 cup coarse kosher salt in large glass bowl. Stir to mix. Cover and let stand in cool place at least 12 hours and up to 1 day, stirring occasionally.
Drain tomato mixture in large colander. Rinse with cold water; let drain well, at least 30 minutes. Using hands, squeeze any excess liquid from tomato mixture.
Combine tomato mixture, 1 1/2 teaspoons coarse salt, and next 5 ingredients in large pot. Stir over medium-high heat until sugar dissolves. Bring to boil. Reduce heat to medium-low; simmer until almost all liquid evaporates, stirring frequently, about 1 hour 10 minutes. Remove from heat.
Ladle mixture into 6 hot clean 1/2-pint glass canning jars, leaving 1/2-inch space at top of jars. Remove air bubbles. Wipe jar threads and rims with clean damp cloth. Cover with hot lids; apply screw bands. Process jars in pot of boiling water 10 minutes. Cool jars completely. Store in cool dark place up to 1 year.
From Bon Appétit, Oct. 2008, by Jill Silverman Hough.