Apex domains cannot have CNAME records.
Question and response
Question
dig SURNET.ru. NS
Answer
SURNET.ru. 3 NS ns5.tmn.ru.
SURNET.ru. 3 NS ns6.tmn.ru.
Authority
The response has no authority records.
Additional
ns5.tmn.ru. 3 A 213.59.199.162
ns6.tmn.ru. 3 A 188.128.82.234
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0