Apex domains cannot have CNAME records.
Question and response
Question
dig sillywho.com. NS
Answer
sillywho.com. 5 NS ns-867.awsdns-44.net.
sillywho.com. 5 NS ns-1805.awsdns-33.co.uk.
sillywho.com. 5 NS ns-660.awsdns-18.net.
sillywho.com. 5 NS ns-1179.awsdns-19.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0