Mother's Rhubarb Relish

From the Green Shutters Cookbook Lunenburg

4 cups diced rhubarb
4 cups diced onions
6 cups brown sugar
2 cups cider vinegar
1 tsp ground cinnamon
1/2 tsp ground cloves
1 tsp ground allspice
1/2 tsp pepper
2 tsp salt

Measure all ingredients into a large pot. Stir to combine.
Simmer over low heat until the mixture is reduced by half and thickened, approximately 2 hours.
Remove from heat and put in sterilized bottles and seal. Serve chilled. Makes 8 cups