Grind onions, cabbage, green tomatoes, green peppers, and red peppers.

Sprinkle ground vegetables with salt and let stand overnight.

Rinse and drain the salted vegetables thoroughly.

In a large pot, combine sugar, celery seed, turmeric, vinegar, and water.

Add the rinsed and drained vegetable mixture to the pot.

Heat the mixture to boiling, stirring occasionally.

Once boiling, reduce heat and simmer for 3 minutes.

Carefully ladle the hot relish into hot, sterilized jars, leaving appropriate headspace.

Seal the jars according to canning instructions.