Apex domains cannot have CNAME records.
Question and response
Question
dig ip-addr.inexio.net. NS
Answer
ip-addr.inexio.net. 5 NS ns3.inexio.net.
ip-addr.inexio.net. 5 NS ns1.inexio.net.
ip-addr.inexio.net. 5 NS ns2.inexio.net.
Authority
The response has no authority records.
Additional
ns1.inexio.net. 5 A 131.117.146.40
ns2.inexio.net. 5 A 188.210.43.194
ns3.inexio.net. 5 A 217.19.180.251
ns1.inexio.net. 5 AAAA 2a01:5c0:6:38:0:0:0:40
ns2.inexio.net. 5 AAAA 2a01:5c0:6:8:0:0:0:194
ns3.inexio.net. 5 AAAA 2a00:1f08:4047:0:0:0:0:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0