A saffron bun, Cornish tea treat bun or revel bun, Swedish lussebulle or lussekatt, Norwegian lussekatt, is a rich, spiced yeast-leavened sweet bun that is flavoured with saffron and cinnamon or nutmeg and contains currants similar to a teacake. The main ingredients are plain flour, butter, yeast, caster sugar, currants and sultanas. Larger versions baked in a loaf tin are known as saffron cake. In parts of Britain, the buns were traditionally baked on sycamore leaves and dusted with powdered sugar.