Step 1

Grind tomatoes, onions, and bell peppers in a food processor in separate batches. Line a colander with cheesecloth and set it in a large bowl. Pour the ground vegetables into the lined colander and drain for 1 hour.

Step 2

Mix drained vegetable mixture, sugar, vinegar, celery seed, mustard seed, and salt in a large stockpot over high heat and bring it to a boil. Bring the heat down to low. Simmer for 5 minutes, stirring regularly.

Step 3

Place the relish in sterilized glass jars, filling them to the top, and cover tightly. Ensure there are no air pockets throughout.

Step 4

Place a rack in a large stockpot and fill it halfway with water; bring to a boil. Lower the jars into the pot, allowing 2 inches of space in between. The jars should be covered by 2 inches of water. Add more boiling water if needed.

Step 5

Bring the water to a full boil. Cover the stockpot and cook for 30 minutes.

Step 6

Remove the jars from the pot, place them on a clothed surface, and let them cool. To ensure the seal is tight, press the lids with your finger. The lid should not move at all. Store green tomato relish for up to 1 year.

Step 7

Clean the jars and lids thoroughly with soap and water.

Step 8

Preheat the oven to 110 degrees Fahrenheit. Place mason jars upright on a baking dish. Place them in the oven for 15 minutes or until dry.

Step 9

Meanwhile, boil the lids for 5 minutes. Set them on a wire rack to air dry.