This Rhubarb Tart features a tangy rhubarb curd nestled in a buttery shortbread crust. The rhubarb sauce is cooked and pureed for a smooth texture, then combined with a lemon-flavored curd before baking to a perfect set. Finished with a light dusting of confectioners' sugar, this tart is a bright and refreshing dessert perfect for spring or summer gatherings.