Apex domains cannot have CNAME records.
Question and response
Question
dig GTCONLINE.RU. NS
Answer
gtconline.ru. 5 NS ns3.gtconline.ru.
gtconline.ru. 5 NS ns1.gtconline.ru.
gtconline.ru. 5 NS ns2.gtconline.ru.
Authority
The response has no authority records.
Additional
ns1.GTCONLINE.RU. 5 A 87.237.137.2
ns2.GTCONLINE.RU. 5 A 87.237.139.42
ns3.GTCONLINE.RU. 5 A 31.186.62.135
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0