Rinse the 1 lb rhubarb and trim the the ends (the leaves are toxic.) Slice it into 1 inch pieces and put in a heavy bottomed pot along with the 1/2 cup sugar. Add 2 tablespoons of water and a squeeze of fresh lemon, and stir to combine.
Heat, stirring constantly, until the rhubarb starts to give off juice and the mixture comes to a boil. Boil gently for about 15-20 minutes, until the rhubarb is soft and mostly broken down.
Puree the mixture in a blender or food processor. Get it as smooth as you can. Note: Be careful when pureeing hot foods, as they can 'explode' up through the spout of the processor or blender. Make sure the top is on securely, and that it is vented.
Put the puree back on the stove and bring to a boil, then turn down the heat and let it gently bubble away until reduced and thickened about another 20 minutes or so, Stir often, and be careful not to let the fruit scorch. When the rhubarb butter is getting close to done it will darken a bit and get glossier. Your butter is done when you can drag your spoon across the bottom of the pan and the jam doesn't fill in the space. The fruit butter will thicken even further upon chilling. (See the post for photos and details.)
Spoon the finished butter into a glass jar. Let cool, then cap and refrigerate. It will thicken further as it cools. You will have about a one and a half cups.
Notes
If you want to make a larger batch, you can freeze this. I just keep it in the fridge, it will be scarfed up within a couple of weeks.
There is no firm rule about how long to cook the pureed fruit. The longer you cook it and reduce it down, the thicker it will be. It's a matter of personal taste.
You can add a splash of vanilla (or the seeds of a vanilla bean) to your butter at the very end, if you like.
You can also add a small amount of cinnamon or cardamom. Add it once the rhubarb has been pureed. Start with 1/4 teaspoon and add more to taste.
*This recipe was first published in 2014, and was re-tested, updated, and rephotographed in 2024.
Nutritional information is provided as a courtesy and is an estimate only. This information comes from online calculators. Although The View from Great Island attempts to provide accurate nutritional information, these figures are only estimates.
Did You Make This?We love seeing what you've made! Tag us on social media at @theviewfromgreatisland for a chance to be featured.