Rhubarb is one of the best treats of spring and early summer. These long stalks are technically part of the vegetable family, despite a U.S. court ruling in 1947 that classified it as a fruit—because it's typically eaten with dessert.
But that's neither here nor there. Its tart and tangy flavor makes it ideal for combining with sugar and sweeter fruits (like strawberries), and baking into pies and cakes. While we'll always love a good and gooey rhubarb pie, we don't always have time for a full-on baking project. Enter: rhubarb sauce. Sauce is one of the simplest, quickest ways to coax a versatile dessert from your rhubarb. It's infinitely customizable, and is equally delicious spooned over yogurt, drizzled over ice cream, stirred into oatmeal, and so much more. Here's how to go from stalk to sauce in 30 minutes flat.
Rhubarb stalks vary in size; they can be as thin as your pinkie finger or a couple inches wide. This doesn't matter for the purpose of sauce. Just rinse the stalks clean (discard the leaves!) and chop them roughly into 1-inch pieces. Add them to a medium to medium-large sauce pot, even if you're only making a small batch. The sauce will bubble and spit as it cooks.
At its most basic, all rhubarb sauce needs is rhubarb and sugar. But it provides such a great blank canvas for customization, why not play around with flavors? Rhubarb plays well with vanilla (add a split bean to your pot), ginger (peel and mince fresh a tablespoon or so of ginger root), cardamom (mix in a couple of crushed pods), and, of course, other berries (chop and toss 'em in, too). If using extracts, like vanilla or almond, don't add them until the sauce has finished cooking. The same goes for citrus zest, which can become bitter if cooked for too long.
This is not the time to go sugar-free. Not only does rhubarb need sweetness to temper its tart flavor, the sugar helps break down the fibrous, stringy stalks. A good starting point is to use a scant 1 cup granulated sugar for 4 cups of chopped rhubarb. Adjust according to your preferences.
Add a splash of water to your pot to help things get started, but there's no need to add more than that. Once the rhubarb starts cooking, it will release liquid into the pot, contributing to a saucy, liquidy consistency. Start over medium-high heat, then lower to a simmer as soon as it begins to bubble or boil aggressively. Keep uncovered and stir occasionally, making sure no sauce sticks to the bottom of the pot. The sauce will become loose and liquid, then evaporate slightly as it reduces.
The rhubarb will have simmered into a sauce within 30 minutes. Remove it from the heat and let it cool completely. It will thicken and set more as it comes to room temperature. Your sauce will keep for a couple of weeks in the fridge, and also freezes beautifully.