There are many local recipes, and the basic recipe has changed over time. In Medieval times, the cake was a mixture of fruits and nuts encased in pastry and coated with a saffron glaze. An 1892 article from The Gentleman's Magazine describes leftover Christmas pudding wrapped in the remains of unleavened dough from Lent, which was first boiled and then baked. Modern recipes tend toward fruitcake topped with (and sometimes also filled with) a layer of marzipan, then decorated with flowers or marzipan balls.
Etymology: probably from Latin simila, the fine wheat flour used to make the cake. The exact origin of the cake is unclear; it is not named after Lambert Simnel, because references to the cake predate him.