Apex domains cannot have CNAME records.
Question and response
Question
dig magento.cloud. NS
Answer
magento.cloud. 1 NS ns-1.awsdns-00.com.
magento.cloud. 1 NS ns-1195.awsdns-21.org.
magento.cloud. 1 NS ns-551.awsdns-04.net.
magento.cloud. 1 NS ns-1668.awsdns-16.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0