Apex domains cannot have CNAME records.
Question and response
Question
dig PIRIX.ru. NS
Answer
PIRIX.ru. 2 NS ns01.comfortel.pro.
PIRIX.ru. 2 NS ns02.comfortel.pro.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0