8 lbs. tomatoes (about 24 medium tomatoes)
1/2 cup chopped onion
1/4 tsp. cayenne pepper
1 cup sugar
1 cup white vinegar
1-1/2 inches of stick cinnamon, broken into pieces
1-1/2 tsp. whole cloves
1 tsp. celery seed
1/4 cup lemon juice
1 tsp. salt
Core and quarter your tomatoes. In an 8 to 10 quart kettle, combine the tomatoes, onion and cayenne pepper. Bring to boiling and reduce the heat. Boil gently, uncovered, for about 15 minutes, stirring often. Press through a food mill or a sturdy, fine-mesh sieve (one that will allow the tomato pulp to pass through). Discard the seeds and skins. You should have about 10 cups of pulp remaining.
Return the tomato mixture to the dutch oven and add the sugar. Bring this mixture to a boil and then reduce the heat. Boil gently, uncovered, for 1-1/4 to 2 hours, or until reduced by half, stirring it from time to time. (Use a clean wooden ruler to measure the depth before and after cooking to be able to determine when it is reduced by half.)
In a small saucepan, bring the vinegar, cinnamon, cloves and celery seed to boiling. Remove it from the heat and strain it into the tomato mixture. Discard the spices and stir in the lemon juice and salt. Simmer about 40 minutes, or until your tomato sauce has reached your desired consistency.
Ladle the ketchup into hot, clean half-pint canning jars, leaving a 1/2 inch head space. Wipe the jar rims clean, adjust the lids and process in a boiling water canner for 15 minutes (start timing after the water covering the jars has returned to boiling.)
Remove the hars from the canner and cool them on wire racks. This should give you 3 half-pint jars of a very tasty ketchup!