Make sweet green tomato relish by grinding green tomatoes with red and green bell peppers and onions and allowing to drain. Season the relish with celery seed, mustard seed and salt, and then simmer with sugar and cider vinegar. Store in sterilized jars. A recipe is available on AllRecipes.com
Halve and seed 3 red and 3 green bell peppers. Roughly grind 24 large green tomatoes with 12 large onions and the bell peppers in a food processor, and set the mixture in a cheesecloth-lined colander to drain for 1 hour. Transfer the mixture to a stockpot and add 3 tablespoons celery seed, 3 tablespoons mustard seed, 1 tablespoon salt, 5 cups white sugar and 2 cups cider vinegar. Bring to a boil, and then simmer for 5 minutes over low heat while stirring.
Pour the relish into sterilized jars, packing the relish tightly so there are no bubbles or spaces. Secure lids on the jars and process in boiling water for 30 minutes to kill any bacteria or spores. Remove the jars from the pot and allow to cool. Press the tops of the lids to ensure they do not move up and down and are therefore sealed properly. Keep the relish for up to 1 year.