How to Make It
In a large saucepan, combine all of the ingredients. Cook over moderately high heat, stirring constantly and skimming off any foam, until the berries have burst and the rhubarb is soft, 12 minutes. Remove from the heat.
Using a wooden spoon, mash the rhubarb and berries against the side of the pan. Simmer over moderate heat, stirring occasionally, until thickened, 10 minutes. Pour the jam into jars and let cool completely; refrigerate until well chilled.
The jam can be refrigerated for up to 2 weeks.