Foxy - Tunis cake is a Madeira type thing, covered in choc with marzipan fruits on the top. More delicious than it sounds - Madeira cake can be dry - I usually don't like it, but with the choc it somehow worked. Mum used to buy one from M&S every year when I was a kid, but haven't seen one since then.
A capon is a castrated cockerel - the emasculation makes the poor thing edible!