Apex domains cannot have CNAME records.
Question and response
Question
dig alertmedia.com. NS
Answer
alertmedia.com. 3 NS ns-1972.awsdns-54.co.uk.
alertmedia.com. 3 NS ns-825.awsdns-39.net.
alertmedia.com. 3 NS ns-226.awsdns-28.com.
alertmedia.com. 3 NS ns-1077.awsdns-06.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0