Apex domains cannot have CNAME records.
Question and response
Question
dig netcoreglobal.com. NS
Answer
netcoreglobal.com. 5 NS ns-546.awsdns-04.net.
netcoreglobal.com. 5 NS ns-1486.awsdns-57.org.
netcoreglobal.com. 5 NS ns-1971.awsdns-54.co.uk.
netcoreglobal.com. 5 NS ns-492.awsdns-61.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0