Apex domains cannot have CNAME records.
Question and response
Question
dig dpl7x55sqlu2t.cloudfront.net. NS
Answer
dpl7x55sqlu2t.cloudfront.net. 5 NS ns-276.awsdns-34.com.
dpl7x55sqlu2t.cloudfront.net. 5 NS ns-1438.awsdns-51.org.
dpl7x55sqlu2t.cloudfront.net. 5 NS ns-940.awsdns-53.net.
dpl7x55sqlu2t.cloudfront.net. 5 NS ns-1591.awsdns-06.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0