Apex domains cannot have CNAME records.
Question and response
Question
dig barnaul.avantel.ru. NS
Answer
barnaul.avantel.ru. 5 NS ns.avantel.ru.
barnaul.avantel.ru. 5 NS ns.barnaul.avantel.ru.
Authority
The response has no authority records.
Additional
ns.avantel.ru. 5 A 195.49.168.2
ns.barnaul.avantel.ru. 5 A 93.91.172.2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0