Apex domains cannot have CNAME records.
Question and response
Question
dig borzenkov.ru. NS
Answer
borzenkov.ru. 4 NS ns2.spaceweb.ru.
borzenkov.ru. 4 NS ns1.spaceweb.ru.
borzenkov.ru. 4 NS ns4.spaceweb.pro.
borzenkov.ru. 4 NS ns3.spaceweb.pro.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0