4 lb plums, pitted and quartered
8 oz pitted Rainier cherries
1 3/4 cups sugar
1/4 cup lemon juice
Place all ingredients in a 4 quart slow cooker, stir. Turn on low and cook overnight (about 8-10 hrs) with the lid slightly askew to allow for some evaporation to occur. The mixture should be thick and paste-like when ready. If the mixture isn't totally smooth, pulse it with an immersion blender. Prep your jars and lids. Pour the butter in the jars, leaving 1/4 inch headspace. Process in a boiling water bath for 10 minutes.
Yield: about 4 8-oz jars
Note: A great source for canning information is the Blue Book guide to preserving. I highly recommend it for learning how to can. Here are some of my other favorite canning books and supplies.