\xef\xbb\xbf are three invisible junk characters (at least from Apache's perspective) called the Unicode BOM, or byte order mark. Apache thinks that those characters are part of the command that follows right after. This is what you see in the log, though the characters are escaped so they're visible to the naked eye. \xef\xbb\xbfRewriteEngine
Copy the content in any advanced notepad editor which will detect the characters and you can easily remove them.
If you are not able to see these characters, remove this file completely and write again.
