Apex domains cannot have CNAME records.
Question and response
Question
dig NIC.GDN. NS
Answer
NIC.GDN. 5 NS ns3.NIC.GDN.
NIC.GDN. 5 NS ns1.NIC.GDN.
Authority
The response has no authority records.
Additional
ns1.nic.gdn. 116614 A 194.0.25.18
ns3.nic.gdn. 164853 A 194.0.26.11
ns1.nic.gdn. 116614 AAAA 2001:678:20:0:0:0:0:18
ns3.nic.gdn. 164853 AAAA 2001:67c:10e0:0:0:0:0:11
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0