Apex domains cannot have CNAME records.
Question and response
Question
dig AVMAIL.ru. NS
Answer
avmail.ru. 2 NS dnsproxy1.fm.nic.ru.
avmail.ru. 2 NS dnsproxy2.fm.nic.ru.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0