Apex domains cannot have CNAME records.
Question and response
Question
dig NTT.RU. NS
Answer
ntt.ru. 5 NS dns.ntt.ru.
ntt.ru. 5 NS ns4-l2.nic.ru.
ntt.ru. 5 NS ns4.nic.ru.
ntt.ru. 5 NS ns8.nic.ru.
ntt.ru. 5 NS ns.ntt.ru.
ntt.ru. 5 NS ns1.ntt.ru.
Authority
The response has no authority records.
Additional
ns.ntt.RU. 5 A 195.28.32.3
ns1.ntt.RU. 5 A 195.28.33.1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0