Apex domains cannot have CNAME records.
Question and response
Question
dig cloud4j.com. NS
Answer
cloud4j.com. 5 NS ns-509.awsdns-63.com.
cloud4j.com. 5 NS ns-1910.awsdns-46.co.uk.
cloud4j.com. 5 NS ns-1226.awsdns-25.org.
cloud4j.com. 5 NS ns-607.awsdns-11.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0