Apex domains cannot have CNAME records.
Question and response
Question
dig AVMAILER.RU. NS
Answer
AVMAILER.RU. 5 NS ns1.AVMAILER.RU.
AVMAILER.RU. 5 NS ns2.AVMAILER.RU.
Authority
The response has no authority records.
Additional
ns1.avmailer.ru. 5 A 93.91.168.162
ns2.avmailer.ru. 5 A 95.170.144.167
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0