Meanwhile, in a small saucepan over medium heat, bring the vinegar, sugar, cinnamon, mustard seeds, cumin seeds, cloves, celery seeds, peppercorns, dry mustard, cayenne and salt to a boil. Stir to dissolve the sugar, turn off the heat, and let it sit while the tomatoes continue to reduce. When tomatoes are reduced by half, strain the spice-infused vinegar into the tomatoes, discarding the spices. Continue to simmer the ketchup, stirring often, until thick, 20 to 30 minutes (or more if necessary). Taste for salt and spice, and adjust to your liking.