Puree the prunes and water in a blender until smooth. This will have a strong flavor, and thus is best suited to heavily spiced baked goods (i.e. gingerbread) or chocolate-based desserts. Substitute other dried fruit such as apples, peaches, and apricots for half of the prunes for a flavor and nutrient variation.
Recipe by Go Dairy Free at https://www.godairyfree.org/recipes/cream-and-butter-subs/prune-dried-fruit-puree-butter-baking-substitute