Rhubarb and raspberries are a terrific combo, as good as the familiar strawberry-rhubarb team. This quick and easy sauce is a favorite. Use it to flavor plain yogurt, mix into smoothies, or as a sauce for ice cream and cakes. It can be varied by using orange juice instead of water, and ginger has a natural affinity for these fruits. If you want the sauce to be more elegant, pass it through a fine mesh sieve before serving.
From The Earthbound Cook: 250 Recipes for Delicious Food and a Healthy Planet by Myra Goodman
Combine the sugar and 1/2 cup water in a medium-size saucepan and cook over high heat, stirring frequently, until the sugar is dissolved. Then reduce the heat to low and add the rhubarb. Cook, stirring occasionally, until the rhubarb is tender and soft, about 5 minutes.
Add the raspberries and cook for 1 minute, mashing them lightly with a spoon. (The berries will fall apart as soon as they are heated.)
Remove the pan from the heat, stir in the lemon juice, and let the sauce cool.
Serve at room temperature or chilled with the Raspberry Yogurt Panna Cotta. The sauce can be refrigerated, covered, for up to 5 days. It's also delicious served warm with other desserts.