Apex domains cannot have CNAME records.
Question and response
Question
dig firstvds.RU. NS
Answer
firstvds.RU. 5 NS ns1.ddos-guard.net.
firstvds.RU. 5 NS ns2.ddos-guard.net.
Authority
The response has no authority records.
Additional
ns1.ddos-guard.net. 5 A 186.2.170.100
ns2.ddos-guard.net. 5 A 185.129.100.200
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0