Pour prepared tomatoes in a stock pot. Bring to boil, reduce to simmer.

Saute chopped onions until browned and beginning to caramelize. Add garlic near end, saute. Puree these and some of the vinegar in mini food processor or stick blender. Add smoothed mixture to stock pot.

Place celery seed and ground black pepper in a cheesecloth pouch tied with string and put in stock pot.

Add remaining vinegar, cayenne, salt, brown sugar, mustard, cloces and Worcestershire Sauce.

Simmer very slowly (to keep the tomatoes from burning), until the volume is reduced by about one-half. It should have the consistency of thick tomato sauce. This step may take six hours or more.

If the sauce is too chunky, run it in batches through a blender. Return to the stockpot and simmer until the mixture is the consistency of thin commercial ketchup. This step may take three hours or more.

Correct the seasoning with salt, pepper, sugar and Worcestershire.

Can via water bath canning process.