Apex domains cannot have CNAME records.
Question and response
Question
dig ssvec.az.wi-power.com. NS
Answer
ssvec.az.wi-power.com. 5 NS ns1.coslink.net.
ssvec.az.wi-power.com. 5 NS ns1.powerc.net.
ssvec.az.wi-power.com. 5 NS ns2.coslink.net.
Authority
The response has no authority records.
Additional
ns1.powerc.net. 4 A 64.68.224.10
ns1.coslink.net. 4 A 64.68.224.8
ns2.coslink.net. 4 A 64.68.248.10
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0