Apex domains cannot have CNAME records.
Question and response
Question
dig 228.167.195.in-addr.arpa. NS
Answer
228.167.195.in-addr.arpa. 5 NS nsrev01.dns.sfr.net.
228.167.195.in-addr.arpa. 5 NS nsrev00.dns.sfr.net.
Authority
The response has no authority records.
Additional
nsrev00.dns.sfr.net. 5 A 109.0.66.8
nsrev01.dns.sfr.net. 5 A 109.0.66.18
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0