Apex domains cannot have CNAME records.
Question and response
Question
dig 119.133.31.in-addr.arpa. NS
Answer
119.133.31.in-addr.arpa. 5 NS ns1.enterra.dp.ua.
119.133.31.in-addr.arpa. 5 NS ns.enterra.dp.ua.
Authority
The response has no authority records.
Additional
ns.enterra.dp.ua. 5 A 91.212.80.120
ns1.enterra.dp.ua. 5 A 91.212.80.113
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0