tarte tatin an upside-down French apple tart (or pie, depending on how one looks at it). Into the baking tin goes first a layer of sugar, then slices of apple, pre-cooked a little in butter, and finally the pastry. After being baked, the whole is turned out upside down. The apple juices then soak down into the pastry and the sugar has caramelized, giving a lovely golden topping.
The Larousse gastronomique explains that the name commemorates the Tatin sisters, who popularized it in their restaurant at Lamotte-Beuvron, to the south of Orléans, in the early 20th century. Later in the century, chefs devised variations, using pear, pineapple, or rhubarb, to give but three examples.