Apex domains cannot have CNAME records.
Question and response
Question
dig AU. NS
Answer
au. 5 NS t.au.
au. 5 NS s.au.
au. 5 NS a.au.
au. 5 NS q.au.
au. 5 NS r.au.
Authority
The response has no authority records.
Additional
a.au. 149647 A 58.65.254.1
q.au. 138430 A 65.22.196.1
r.au. 139323 A 65.22.197.1
s.au. 121504 A 65.22.198.1
t.au. 118335 A 65.22.199.1
a.au. 149647 AAAA 2407:6e00:254:0:0:0:0:1
q.au. 138430 AAAA 2a01:8840:be:0:0:0:0:1
r.au. 139323 AAAA 2a01:8840:bf:0:0:0:0:1
s.au. 121504 AAAA 2a01:8840:c0:0:0:0:0:1
t.au. 118335 AAAA 2a01:8840:c1:0:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0