Wash 2 pounds of green tomatoes, 1 cup of onions, and 1 cup of bell peppers. Chop into small pieces.

In a large pot, combine the tomatoes, onions, bell peppers, 2 cups of vinegar, 1 cup of sugar, 1 tablespoon of salt, 1 teaspoon of celery seed, 1 teaspoon of turmeric, and 1 teaspoon of red pepper flakes. Stir well.

Bring the mixture to a boil over medium-high heat, stirring frequently. Boil for about 10 minutes.

Reduce heat to medium-low and let the mixture simmer for 60 to 90 minutes, stirring occasionally, until thickened.

If canning, sterilize 4 to 5 jars and lids by boiling for 10 minutes.

Ladle the hot relish into jars, leaving ½ inch headspace. Wipe rims and seal jars. Process in a boiling water bath for 15 minutes.

Cool jars completely on a towel or rack. Check seals; store in a cool, dark place.