Apex domains cannot have CNAME records.
Question and response
Question
dig fondoo.org. NS
Answer
fondoo.org. 5 NS ns-722.awsdns-26.net.
fondoo.org. 5 NS ns-1136.awsdns-14.org.
fondoo.org. 5 NS ns-101.awsdns-12.com.
fondoo.org. 5 NS ns-1067.awsdns-05.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0