I was in a churrasqueira and the gent behind the counter was asking if I wanted my bifanas on bread. And what he said (twice because I literally did not understand) sounded like “em pô”. As I left, he said boa noiche. So I assume this is a Brazilian variant but wanted to as if this is a common pronunciation?
@MeuDeus, boa noitche sounds like Brazilian Portuguese, yes. Regarding the word pão, I don’t know what you heard exactly, so there’s not much I can say. To my ears, the average PT-PT and PT-BR pronunciations of that word don’t really differ much, but maybe you found an exception 
Boa noite. Here in Biana do Castelo it’s definitely another word. Not pão, but something like pang. It makes learning Portuguese even more “interesting” ….