Apex domains cannot have CNAME records.
Question and response
Question
dig enverus.com. NS
Answer
enverus.com. 5 NS ns-1624.awsdns-11.co.uk.
enverus.com. 5 NS ns-1365.awsdns-42.org.
enverus.com. 5 NS ns-510.awsdns-63.com.
enverus.com. 5 NS ns-812.awsdns-37.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0