1Wash tomatoes, cut out stem end, and squeeze to get ride of seeds and some liquid. Combine quartered tomatoes with onions and pepper in large kettle; cook uncovered 20–25 minutes, stirring occasionally. While tomatoes are cooking, combine in small saucepan: vinegar, cinnamon stick, cloves, allspice, and celery seed. Bring just to a boil; remove from heat and let stand 15 minutes. Put tomatoes through food mill, allowing them to sit first to drain off excess liquid; discard liquid. Blend puree in blender on high speed 30–45 seconds. In 2-quart kettle, combine puree, sugar, and salt. Strain vinegar and spice mixture through fine strainer or cheesecloth; stir into puree. Boil slowly, uncovered, until thick as commercial catsup, 30–45 minutes, stirring frequently. To test for water content, put a tsp. of catsup on a cold plate. If too watery, the water will separate from the puree right away. Continue cooking. If it continues to be too watery, stir in a bit of corn starch and water. Pour into hot sterilized jars; seal. Process in boiling water bath for 10 minutes. Note: Stir frequently as it’s apt to scorch; keep heat medium-low.