Apex domains cannot have CNAME records.
Question and response
Question
dig synsue.com. NS
Answer
synsue.com. 5 NS ns-1947.awsdns-51.co.uk.
synsue.com. 5 NS ns-184.awsdns-23.com.
synsue.com. 5 NS ns-578.awsdns-08.net.
synsue.com. 5 NS ns-810.awsdns-37.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0