Apex domains cannot have CNAME records.
Question and response
Question
dig sunnet.net.ru. NS
Answer
sunnet.net.ru. 5 NS ns2.majordomo.ru.
sunnet.net.ru. 5 NS ns.majordomo.ru.
sunnet.net.ru. 5 NS ns3.majordomo.ru.
Authority
The response has no authority records.
Additional
ns.majordomo.ru. 5 A 78.108.80.80
ns2.majordomo.ru. 5 A 78.108.88.164
ns3.majordomo.ru. 5 A 78.108.80.90
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0