Apex domains cannot have CNAME records.
Question and response
Question
dig xenix.io. NS
Answer
xenix.io. 5 NS ns1-us-ewr.xenixlabs.net.
xenix.io. 5 NS ns2-nl-ams.xenixlabs.net.
xenix.io. 5 NS ns3-us-lax.xenixlabs.net.
xenix.io. 5 NS ns4-sg-sin.xenixlabs.net.
xenix.io. 5 NS ns5-br-gru.xenixlabs.net.
Authority
The response has no authority records.
Additional
ns1-us-ewr.xenixlabs.net. 5 A 45.79.187.224
ns2-nl-ams.xenixlabs.net. 5 A 172.233.58.135
ns3-us-lax.xenixlabs.net. 5 A 172.236.230.86
ns4-sg-sin.xenixlabs.net. 5 A 172.237.74.138
ns5-br-gru.xenixlabs.net. 5 A 172.233.21.97
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0