Apex domains cannot have CNAME records.
Question and response
Question
dig sintec.ru. NS
Answer
sintec.ru. 5 NS ns2.afraid.org.
sintec.ru. 5 NS ext01-1.sintec.ru.
Authority
The response has no authority records.
Additional
ext01-1.sintec.ru. 5 A 77.95.130.178
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0