Apex domains cannot have CNAME records.
Question and response
Question
dig SCO.RU. NS
Answer
sco.ru. 5 NS ns.sco.ru.
sco.ru. 5 NS ns2.sco.ru.
Authority
The response has no authority records.
Additional
ns.sco.ru. 5 A 79.110.255.18
ns2.sco.ru. 5 A 79.110.240.2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0