Apex domains cannot have CNAME records.
Question and response
Question
dig zwing.site. NS
Answer
zwing.site. 5 NS ns-2013.awsdns-59.co.uk.
zwing.site. 5 NS ns-2012.awsdns-59.co.uk.
zwing.site. 5 NS ns-539.awsdns-03.net.
zwing.site. 5 NS ns-659.awsdns-18.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0