Technically a vegetable, rhubarb is treated like a fruit and is traditionally paired with strawberries, which complement its tart, fruity flavor. Rhubarb comes in two types. Field rhubarb, most often available in late spring, is cherry-red and has a more pronounced flavor than its hothouse kin. Hothouse rhubarb is bright pink and is usually in the market year-round. To avoid a stringy filling, slice the rhubarb no wider than 1/2 inch thick. If the outside of the stalks are stringy, remove the strings with a vegetable peeler. Rhubarb leaves are mildly toxic and should always be discarded.