Apex domains cannot have CNAME records.
Question and response
Question
dig imt.su. NS
Answer
imt.su. 3 NS ns1.imt.ru.
imt.su. 3 NS ns2.imt.ru.
Authority
The response has no authority records.
Additional
ns1.imt.ru. 4 A 212.16.8.99
ns2.imt.ru. 4 A 212.16.1.22
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0