Apex domains cannot have CNAME records.
Question and response
Question
dig csod.com. NS
Answer
csod.com. 5 NS ns2.p202.dns.oraclecloud.net.
csod.com. 5 NS ns3.p202.dns.oraclecloud.net.
csod.com. 5 NS teomgtadns-two2.csodmgmt.corp.
csod.com. 5 NS udns1.ultradns.net.
csod.com. 5 NS udns2.ultradns.net.
csod.com. 5 NS ns1.p202.dns.oraclecloud.net.
csod.com. 5 NS ns4.p202.dns.oraclecloud.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0