I'm looking for a book called "Aztec"(?)?

The book I'm looking for is the following: it was the actual testimony of an Aztec man as recorded by Catholic friers a couple hundred years ago. After the man's testimony reached the King of Spain, the King demanded that the Aztec man not be harmed. However, the Aztec was already dead - killed for not converting to Christianity. I'm looking for the book that contains his testimony. I believe that it is called "Aztec" but I'm unable to actually find it on Amazon.com or anywhere else. If someone can help me locate it, that would be great. If you can find it online, please give me the link. Thank you!