Apex domains cannot have CNAME records.
Question and response
Question
dig kowabunga.net. NS
Answer
kowabunga.net. 5 NS ns-2030.awsdns-61.co.uk.
kowabunga.net. 5 NS ns-1272.awsdns-31.org.
kowabunga.net. 5 NS ns-68.awsdns-08.com.
kowabunga.net. 5 NS ns-735.awsdns-27.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0