Apex domains cannot have CNAME records.
Question and response
Question
dig d3lb4vzijwqdph.cloudfront.net. NS
Answer
d3lb4vzijwqdph.cloudfront.net. 5 NS ns-775.awsdns-32.net.
d3lb4vzijwqdph.cloudfront.net. 5 NS ns-1793.awsdns-32.co.uk.
d3lb4vzijwqdph.cloudfront.net. 5 NS ns-426.awsdns-53.com.
d3lb4vzijwqdph.cloudfront.net. 5 NS ns-1145.awsdns-15.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0