Apex domains cannot have CNAME records.
Question and response
Question
dig don57i5udog9x.cloudfront.net. NS
Answer
don57i5udog9x.cloudfront.net. 5 NS ns-1338.awsdns-39.org.
don57i5udog9x.cloudfront.net. 5 NS ns-2001.awsdns-58.co.uk.
don57i5udog9x.cloudfront.net. 5 NS ns-229.awsdns-28.com.
don57i5udog9x.cloudfront.net. 5 NS ns-591.awsdns-09.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0