Apex domains cannot have CNAME records.
Question and response
Question
dig greenviewdata.com. NS
Answer
greenviewdata.com. 5 NS ns-720.awsdns-26.net.
greenviewdata.com. 5 NS ns-424.awsdns-53.com.
greenviewdata.com. 5 NS ns-1641.awsdns-13.co.uk.
greenviewdata.com. 5 NS ns-1084.awsdns-07.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0