Apex domains cannot have CNAME records.
Question and response
Question
dig testuj.org. NS
Answer
testuj.org. 4 NS ns-1622.awsdns-10.co.uk.
testuj.org. 4 NS ns-1956.awsdns-52.co.uk.
testuj.org. 4 NS ns-1030.awsdns-00.org.
testuj.org. 4 NS ns-1275.awsdns-31.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0