Combine tomatoes, onions, garlic, hot pepper flakes and celery seeds in a large stainless steel saucepan. Bring to a boil over high heat, stirring constantly. Reduce heat, cover and boil gently until vegetables are soft, about 30 minutes.

Transfer mixture, working in batches, to a food mill to extract liquid and pulp. This can also be done using a sieve placed over a bowl, press with the back of a spoon to extract all the liquid and pulp. Discard solids.

Return liquid and pulp to saucepan. Add brown sugar, vinegar, lemon juice, salt, mace, mustard, ginger and cinnamon. Return to a boil over medium-high heat, stirring occasionally. Reduce heat and boil gently, stirring frequently, until mixture is thickened to the consistency of a thin commercial barbecue sauce, about 30-45 minutes.

Prepare boiling water canner. Heat jars in simmering water until ready for use. Do not boil. Wash lids in warm soapy water and set bands aside.

Ladle hot sauce into a hot jar leaving a ½ inch headspace. Remove air bubbles. Wipe jar rim. Center lid on jar and apply band, adjust to fingertip tight. Place jar in boiling-water canner. Repeat until all jars are filled.

Water must cover jars by 1 inch. Adjust heat to medium-high, cover canner, and bring water to a rolling boil. Process pint jars for 20 minutes, adjusting for altitude. Turn off heat and remove cover. Let jars cool 5 minutes. Remove jars from canner; do not retighten bands if loose. Cool 12-24 hours. Check lids for seal, they should not flex when center is pressed.