catsup

12 lb (6 kg) tomatoes
1 Tbsp olive oil
3 yellow onions, coarsely chopped
3 small red bell peppers, seeded and coarsely chopped
4 cloves garlic, lightly crushed
1 cinnamon stick, crushed
1 Tbsp celery seed
1 Tbsp mustard seed
1 1/2 tsp whole allspice
1 1/2 tsp whole cloves
1/2 tsp peppercorns
1/2 tsp red pepper flakes
1 1/2 cups (12 fl oz/375 ml) cider vinegar
2 Tbsp brown sugar
1 Tbsp molasses
3 Tbsp corn syrup
1 1/2 tsp salt (optional)

Have ready hot, sterilized jars and their lids.
Blanch, peel, and core the tomatoes, then cut into quarters. In a large nonreactive saucepan over medium-low heat, warm the olive oil. Add the onions and peppers and cook until tender, about 5 minutes. Add the minced garlic and cook another 2 minutes. Add the tomatoes and cook until tender, about 30 minutes.
Meanwhile, place the spices on a square of cheesecloth (muslin), bring the corners together, and tie with kitchen string. In a small nonreactive saucepan, bring the vinegar and cheesecloth bag to a boil over medium-high heat, cover, and remove from the heat.
At this point, I pour the tomato and vegetable mixture into a food processor and process until a fine pulpy texture is achieved. You may bypass this if you wish and go on to pass the tomato mixture through a food mill into a clean nonreactive saucepan. Discard the cheesecloth bag and pour all but 1/4 cup (2 fl oz/60 ml) of the vinegar into the tomato mixture. Stir in the sugar, molasses, corn syrup and the salt. Bring to a boil over high heat, reduce the heat to medium, and simmer, stirring often, until the mixture is reduced by more than half and mounds slightly on a spoon, 45-60 minutes. Taste and adjust the seasoning with salt, sugar, and the remaining vinegar.
Ladle the hot ketchup into the jars, leaving 1/4 inch (6 mm) of headspace. Remove any air bubbles and adjust the headspace, if necessary. Wipe the rims clean and seal tightly with the lids.
Process the jars for 10 minutes in a boiling-water bath. The sealed jars can be stored in a cool, dark place for up to 1 year. If a seal has failed, store the jar in the refrigerator for up to 1 month.