A saffron bun, cornish tea treat bun or revel bun, is a rich, spiced yeast-leavened sweet bun that is flavoured with saffron and contains dried fruit including currants and raisins 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. similar buns are swedish lussebulle or lussekatt, norwegian lussekatt.

Source: Wikipedia