Apex domains cannot have CNAME records.
Question and response
Question
dig ozlabs.org. NS
Answer
ozlabs.org. 5 NS ns.ozlabs.org.
ozlabs.org. 5 NS ns3.ozlabs.org.
ozlabs.org. 5 NS ns4.ozlabs.org.
Authority
The response has no authority records.
Additional
ns.ozlabs.org. 5 A 150.107.74.76
ns3.ozlabs.org. 5 A 66.228.55.133
ns4.ozlabs.org. 5 A 178.79.181.204
ns.ozlabs.org. 5 AAAA 2404:9400:2221:ea00:0:0:0:1
ns3.ozlabs.org. 5 AAAA 2600:3c00:0:0:f03c:91ff:fedf:87f4
ns4.ozlabs.org. 5 AAAA 2a01:7e00:0:0:f03c:91ff:fe61:9fa
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0