Wash, core, and cut tomatoes into approximately one inch squares. *No need to remove peels at this time

Place in a large stockpot and place on medium heat. Heat until tomatoes simmer, stirring occasionally.

Add onions, garlic, pepper, cayenne pepper, sugar, dry mustard and cinnamon to the tomatoes. Let simmer for 20-30 minutes.

Place vinegar and celery seeds in a medium stockpot. Bring to a boil and turn down to a simmer for 30 minutes while the tomatoes are simmering.

Place tomato mixture in the food mill to remove the skin and seeds. Place remaining liquid in a 6 quart crock pot. You may have extra liquid that you can add in later.

Strain the celery seeds out of the vinegar and mix 3 cups of vinegar into the crock pot with the tomato mixture.

If you have extra liquid(s), you will be able to add it to the crockpot as evaporation occurs.

Set crockpot on a low setting with the lid removed or vented. Reduce by half - or to your desired thickness. (I let it sit overnight in the crockpot). The time will vary depending on how hot your crockpot gets. We let ours thicken for 14 hours.

Pour hot ketchup into sterilized and hot half-pint canning jars. Add warm lid and seal with the band. Process in a hot water bath, adjusting for altitude as needed, for 35 minutes for half-pints or pints, and 40 minutes for quarts.