Apex domains cannot have CNAME records.
Question and response
Question
dig INFRA-BRV.RU. NS
Answer
INFRA-BRV.RU. 5 NS kip.ns.cloudflare.com.
INFRA-BRV.RU. 5 NS leah.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0