Apex domains cannot have CNAME records.
Question and response
Question
dig tviinet.ru. NS
Answer
tviinet.ru. 5 NS ns1.tviinet.ru.
tviinet.ru. 5 NS ns2.tviinet.ru.
Authority
The response has no authority records.
Additional
ns1.tviinet.ru. 5 A 176.107.219.41
ns2.tviinet.ru. 5 A 176.107.219.42
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0