Apex domains cannot have CNAME records.
Question and response
Question
dig phishguru.com. NS
Answer
phishguru.com. 4 NS ns-630.awsdns-14.net.
phishguru.com. 4 NS ns-484.awsdns-60.com.
phishguru.com. 4 NS ns-1682.awsdns-18.co.uk.
phishguru.com. 4 NS ns-1350.awsdns-40.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0