Apex domains cannot have CNAME records.
Question and response
Question
dig cavecreek.net. NS
Answer
cavecreek.net. 2 NS ns3.phoenixnap.com.
cavecreek.net. 2 NS ns1.phoenixnap.com.
cavecreek.net. 2 NS ns2.phoenixnap.com.
Authority
The response has no authority records.
Additional
ns1.phoenixnap.com. 5 A 131.153.36.11
ns2.phoenixnap.com. 5 A 131.153.36.13
ns3.phoenixnap.com. 5 A 131.153.36.15
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0