Apex domains cannot have CNAME records.
Question and response
Question
dig scoreperfectgmat.com. NS
Answer
scoreperfectgmat.com. 5 NS ns-1632.awsdns-12.co.uk.
scoreperfectgmat.com. 5 NS ns-825.awsdns-39.net.
scoreperfectgmat.com. 5 NS ns-1721.awsdns-23.co.uk.
scoreperfectgmat.com. 5 NS ns-1706.awsdns-21.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0