Apex domains cannot have CNAME records.
Question and response
Question
dig gazpromtelecom.RU. NS
Answer
gazpromtelecom.ru. 5 NS ns.gazpromtelecom.ru.
gazpromtelecom.ru. 5 NS ns3.gazpromtelecom.ru.
gazpromtelecom.ru. 5 NS ns2.gazpromtelecom.ru.
Authority
The response has no authority records.
Additional
ns.gazpromtelecom.RU. 5 A 87.237.137.2
ns2.gazpromtelecom.RU. 5 A 87.237.139.42
ns3.gazpromtelecom.RU. 5 A 31.186.62.135
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0