Instructions: Wash 4 pint jars. Keep hot until needed. Prepare lids as manufacturer directs.

Combine rhubarb, sugar, vinegar, raisins, onion, ginger, allspice, cinnamon, salt and red pepper flakes. Cook until thick, about 25 minutes. As mixture thickens, stir frequently to prevent sticking.

Ladle hot sauce into 1 hot jar at a time, leaving 1/4 inch head space. Wipe jar rim with a clean, damp cloth. Attach lid. Fill and close remaining jars.

Process in a boiling-water canner for 15 minutes (20 minutes at 1,000 to 3,000 feet; 25 minutes 3,000 to 6,000 feet; 30 minutes above 6,000 feet).

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