Apex domains cannot have CNAME records.
Question and response
Question
dig ocs.ru. NS
Answer
ocs.ru. 5 NS ns.ocs.ru.
ocs.ru. 5 NS cetus.ocs.ru.
Authority
The response has no authority records.
Additional
ns.ocs.ru. 5 A 91.220.11.25
cetus.ocs.ru. 5 A 185.171.101.179
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0