Apex domains cannot have CNAME records.
Question and response
Question
dig mostcom.ru. NS
Answer
mostcom.ru. 1 NS ns1.mostcom.ru.
mostcom.ru. 1 NS ns2.mostcom.ru.
Authority
The response has no authority records.
Additional
ns1.mostcom.ru. 1 A 81.95.134.1
ns2.mostcom.ru. 1 A 81.95.135.1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0