Apex domains cannot have CNAME records.
Question and response
Question
dig dns-auth.net. NS
Answer
dns-auth.net. 5 NS ns2.dns-auth.net.
dns-auth.net. 5 NS ns5.dns-auth.net.
dns-auth.net. 5 NS ns4.dns-auth.net.
dns-auth.net. 5 NS ns1.dns-auth.net.
dns-auth.net. 5 NS ns3.dns-auth.net.
Authority
The response has no authority records.
Additional
ns1.dns-auth.net. 5 A 194.62.181.53
ns2.dns-auth.net. 5 A 194.62.180.53
ns3.dns-auth.net. 5 A 204.16.255.53
ns4.dns-auth.net. 5 A 194.62.180.53
ns5.dns-auth.net. 5 A 194.62.181.53
ns1.dns-auth.net. 5 AAAA 2a07:dc00:1810:0:0:0:0:53
ns2.dns-auth.net. 5 AAAA 2a07:dc00:180:0:0:0:0:53
ns3.dns-auth.net. 5 AAAA 2620:171:802:752d:0:0:0:1
ns4.dns-auth.net. 5 AAAA 2a07:dc00:180:0:0:0:0:53
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0