A lemon tart is a dessert dish, a variation of a tart. They have a pastry shell with a lemon flavoured filling.In the UK, Lemon Tart (also called Tarte au citron) consists of a pastry case (often made in a fluted tart tin) containing a baked lemon custard (usually composed of eggs, sugar, lemon juice and cream). Usually recipes include blind-baking before adding the custard.