Apex domains cannot have CNAME records.
Question and response
Question
dig r.naoum.net. NS
Answer
r.naoum.net. 4 NS ns-1996.awsdns-57.co.uk.
r.naoum.net. 4 NS ns-707.awsdns-24.net.
r.naoum.net. 4 NS ns-120.awsdns-15.com.
r.naoum.net. 4 NS ns-1214.awsdns-23.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0