Apex domains cannot have CNAME records.
Question and response
Question
dig 188.95.193.in-addr.arpa. NS
Answer
188.95.193.in-addr.arpa. 5 NS sec02.ns.esat.net.
188.95.193.in-addr.arpa. 5 NS auth02.ns.esat.net.
Authority
The response has no authority records.
Additional
sec02.ns.esat.net. 5 A 192.111.39.112
auth02.ns.esat.net. 5 A 193.95.142.60
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0