Apex domains cannot have CNAME records.
Question and response
Question
dig COMSTAR.RU. NS
Answer
comstar.ru. 2 NS dns0.mtu.ru.
comstar.ru. 2 NS dns1.mtu.ru.
Authority
The response has no authority records.
Additional
dns0.mtu.ru. 3 A 195.34.32.83
dns1.mtu.ru. 3 A 212.188.8.37
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0