Combine the oil, onions, and jalapenos in a large heavy stockpot over high heat. Cook, stirring, until slightly soft, 2 to 3 minutes. Add the remaining ingredients and bring to a boil. Reduce the heat to medium-low and simmer, stirring occasionally, until the mixture barely coats a wooden spoon, about 6 hours. Strain through a fine-mesh strainer.
Spoon the hot mixture into three hot sterilized pint-size jars, filling to within 1/2 inch of the top. With a clean, damp cloth, wipe the rim and fit with a hot sterilized lid. Tightly screw on the metal ring. Place the jars on a rack, without them touching one another, in a deep canning kettle with boiling water to cover by 1 inch. Cover the kettle and boil for 15 minutes.
Using tongs, remove the jars from the water, place on a clean towel, and let cool completely. During the heat processing, the contents of the jars expand, forcing some of the air out. The remaining air inside contracts as it cools to create a partial vacuum, which pulls the lid tight against the jar rims. The vacuum and the lid’s sealing compound maintain the seal. A popping noise after the contents have cooled indicates that the seal is complete. To test, press the center of the cooled lid. If it stays depressed, the jar is sealed. If not, refrigerate and use the contents within 2 to 3 weeks or reseal with a new flat lid and repeat the hot water bath. Tighten the rings. Store in a cool, dark place and let age for at least 2 weeks before using. Refrigerate after opening; stored in a covered jar or bottle, the sauce will keep indefinitely.
Yield: 3 pints