"Corta o pão."
I don't think "cut the bread" is a proper sentence... bread is sliced as far as i know, that's why they are called slices of bread.
Hm, I think that's a bit pedantic - what if you were cooking and the bread needed to be cut up into small pieces, not sliced? Or you have some bread rolls and want to cut them in half? Anyway it's an example of the way different languages have specific words for different things, in english we specify between the (very similar) actions of 'cut' and 'slice', in portuguese they do not.
I believe slice should be allowed as well. It's a far more common usage in English.