Apex domains cannot have CNAME records.
Question and response
Question
dig nblnet.com. NS
Answer
nblnet.com. 5 NS ns2.cygate.fi.
nblnet.com. 5 NS ns1.cygate.fi.
Authority
The response has no authority records.
Additional
ns1.cygate.fi. 5 A 81.20.229.4
ns2.cygate.fi. 5 A 81.20.224.133
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0