Saint Clement's Cake is a British cake, traditionally associated with the Feast of Saint Clement on Novemeber 23, made with flour, butter, sugar, eggs, orange, and lemon. The oranges and lemons of the cake are believed to be in memory of fruits distributed at the Saint Clement's Day celebrations at the St. Clement Danes church in London.
Note that it is not the same as clementine cake, which has Judeo-Spanish roots.