Apex domains cannot have CNAME records.
Question and response
Question
dig nameserverz.com. NS
Answer
nameserverz.com. 5 NS ns3.nameserverz.com.
nameserverz.com. 5 NS ns1.nameserverz.com.
nameserverz.com. 5 NS ns2.nameserverz.com.
Authority
The response has no authority records.
Additional
ns1.nameserverz.com. 5 A 103.248.176.140
ns2.nameserverz.com. 5 A 202.37.129.10
ns3.nameserverz.com. 5 A 74.50.61.213
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0