Apex domains cannot have CNAME records.
Question and response
Question
dig vernet.SU. NS
Answer
vernet.SU. 5 NS ns2.vernet.SU.
vernet.SU. 5 NS ns.vernet.SU.
Authority
The response has no authority records.
Additional
ns.vernet.su. 5 A 77.91.199.1
ns2.vernet.su. 5 A 77.91.193.205
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0