Nigella Rhubarb Tart is made with rhubarb stalks, all-purpose flour, unsalted butter, ground almonds, caster sugar, vanilla extract, one large egg, cornstarch, ground cinnamon, lemon zest, and Demerara sugar. This British Nigella Rhubarb Tart recipe creates a delicious dessert that takes about 3 hours to prepare and can serve up to 8 people.