Apex domains cannot have CNAME records.
Question and response
Question
dig 203.77.82.in-addr.arpa. NS
Answer
203.77.82.in-addr.arpa. 5 NS ns1.rdsnet.ro.
203.77.82.in-addr.arpa. 5 NS ns2.rdsnet.ro.
Authority
The response has no authority records.
Additional
ns1.rdsnet.ro. 5 A 193.231.236.17
ns2.rdsnet.ro. 5 A 193.231.236.10
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0