Combine the rhubarb, maple syrup, lemon zest, and water in a small saucepan. Bring to a boil over medium-high heat, then reduce heat to medium or medium-low, so that a steady simmer remains. Stir frequently, and cook until the rhubarb has broken down and thickened, about 15 minutes. You may need up to 30 minutes of cooking time.
Remove the rhubarb sauce from heat. It will continue to thicken as it cools, but you can serve it immediately if desired.
Spoon over vanilla ice cream, and enjoy!
Fresh or frozen rhubarb can be used in this recipe.
Nutrition facts are only for the rhubarb sauce and do not include the ice cream.
Store rhubarb sauce in an airtight container in the fridge for a week or more and in the freezer for at least three months. You can also freeze it in an ice cube tray to make individual servings.
Rhubarb sauce can also be used in yogurt, on pancakes, as part of a charcuterie board, on a grilled cheese sandwich, or spooned into oatmeal.