Apex domains cannot have CNAME records.
Question and response
Question
dig optorg.ru. NS
Answer
optorg.ru. 5 NS ns2.optorg.ru.
optorg.ru. 5 NS ns1.optorg.ru.
optorg.ru. 5 NS ns4.optorg.ru.
optorg.ru. 5 NS ns3.optorg.ru.
Authority
The response has no authority records.
Additional
ns3.optorg.ru. 5 A 194.85.62.109
ns4.optorg.ru. 5 A 194.85.62.110
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0