Apex domains cannot have CNAME records.
Question and response
Question
dig nunsys.net. NS
Answer
nunsys.net. 5 NS ns2.nunsys.net.
nunsys.net. 5 NS ns1.nunsys.net.
nunsys.net. 5 NS ns3.nunsys.net.
Authority
The response has no authority records.
Additional
ns1.nunsys.net. 5 A 185.5.236.12
ns2.nunsys.net. 5 A 185.5.236.13
ns3.nunsys.net. 5 A 23.102.31.5
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0