In a food processor or blender, blend the tomatoes until mostly smooth. Mix the tomato puree with the rest of the ingredients in a large stockpot. Heat over medium-high heat and bring to a boil. Reduce the heat and allow to simmer for about an hour, or until the preserves will mound on the back of a spoon without sliding off immediately. Use an immersion blender to smooth out the preserves.
Tip: If you don’t have an immersion blender, you can process the preserves in batches in a food processor or blender. Alternatively, don’t blend the preserves any further, and enjoy the more chunky preserves.
While the preserves cook, prepare for canning. Wash the jars and flat lids with hot, soapy water. Put the jars in the canning pot and fill the pot with hot water. Heat over medium-high heat to keep the jars hot. Place the lids in a heat-proof bowl.
When the preserves are almost done, move some of the boiling water from the canning pot into the heat-proof bowl containing the lids. Line the hot jars up on a folded towel, then pour the water out of the heat-proof bowl and off the lids.
Fill the jars with preserves up to Â¼â€ below the rim. Use a clean towel to wipe any preserves off the rims, then top each jar with a lid and a tightened ring. Place the jars back in the canning pot and make sure they are covered by at least 1 inch of water. Bring to a boil and process for 15 minutes. Place the jars on a folded towel and allow to sit, undisturbed, for 24 hours. Check the seals of the lids after 1 hour. If a seal has not formed, refrigerate the jar immediately.
Try making a grilled cheese and tomato preserves sandwich.