In a large saucepan, combine the rhubarb, sugar, and lemon juice. Cook over medium heat, stirring frequently, until the rhubarb is tender, about 10 minutes.
Stir in the raspberries and strawberries. Cook for another 5 minutes, stirring frequently, until the berries are soft and the mixture is thickened.
Remove from the heat and cool to room temperature. Transfer to an airtight container and store in the refrigerator for up to a week.
Interesting Facts
Rhubarb is a perennial vegetable that is a member of the Polygonaceae family.
The combination of rhubarb and berries is a classic flavor combination that is perfect for jams, pies, and sauces.
Rhubarb-berry jam is a great way to use up excess rhubarb or berries you may have on hand.