Half the hot cross buns and butter them. Soften the butter for a few seconds in the microwave to make this a bit easier. Cut the hot cross buns in half again.
Place a layer of hot cross buns into a 22x10cm (9x4inch) oven proof dish.
Sprinkle some sultanas and Demerara sugar on top. Add another layer of buns, sultanas and sugar, repeat if you have any left.