Apex domains cannot have CNAME records.
Question and response
Question
dig rev.sfr.net. NS
Answer
rev.sfr.net. 5 NS nsrev01.dns.sfr.net.
rev.sfr.net. 5 NS nsrev00.dns.sfr.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0