"In many historically Christian countries, buns are traditionally eaten on Good Friday, with the cross standing as a symbol of the crucifixion. They are believed by some to pre-date Christianity, although the first recorded use of the term "hot cross bun" is not until 1733..."
According to cookery writer Elizabeth David, Protestant English monarchs saw the buns as a dangerous hold-over of Catholic belief in England, being baked from the dough used in making the communion wafer. Protestant England attempted to ban the sale of the buns by bakers but they were too popular, and instead Elizabeth I passed a law permitting bakeries to sell them, but only at Easter and Christmas.
English folklore includes many superstitions surrounding hot cross buns. One of them says that buns baked and served on Good Friday will not spoil or become mouldy during the subsequent year. Another encourages keeping such a bun for medicinal purposes. A piece of it given to someone who is ill is said to help them recover.
Sharing a hot cross bun with another is supposed to ensure friendship throughout the coming year, particularly if "Half for you and half for me, Between us two shall goodwill be" is said at the time. Because of the cross on the buns, some say they should be kissed before being eaten. If taken on a sea voyage, hot cross buns are said to protect against shipwreck. If hung in the kitchen, they are said to protect against fires and ensure that all breads turn out perfectly. The hanging bun is replaced each year.wikipedia