Apex domains cannot have CNAME records.
Question and response
Question
dig us-gov-phoenix-1.ocs.oraclegovcloud.com. NS
Answer
us-gov-phoenix-1.ocs.oraclegovcloud.com. 5 NS ns1.p200.dns.us-gov-phoenix-1.oci.oraclegoviaas.com.
us-gov-phoenix-1.ocs.oraclegovcloud.com. 5 NS ns3.p200.dns.us-gov-phoenix-1.oci.oraclegoviaas.com.
us-gov-phoenix-1.ocs.oraclegovcloud.com. 5 NS ns2.p200.dns.us-gov-phoenix-1.oci.oraclegoviaas.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0