Apex domains cannot have CNAME records.
Question and response
Question
dig astrolabs.biz. NS
Answer
astrolabs.biz. 5 NS tardis.astrocompanies.com.
astrolabs.biz. 5 NS zaphod.astrocompanies.com.
Authority
The response has no authority records.
Additional
tardis.astrocompanies.com. 5 A 192.109.92.21
zaphod.astrocompanies.com. 5 A 192.109.92.20
tardis.astrocompanies.com. 5 AAAA 2607:e580:0:0:0:0:0:5
zaphod.astrocompanies.com. 5 AAAA 2607:e580:0:0:0:0:0:f
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0