Apex domains cannot have CNAME records.
Question and response
Question
dig RZ.ru. NS
Answer
RZ.ru. 5 NS irena.ns.cloudflare.com.
RZ.ru. 5 NS michael.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0