Apex domains cannot have CNAME records.
Question and response
Question
dig netshield.uk. NS
Answer
netshield.uk. 5 NS terry.ns.cloudflare.com.
netshield.uk. 5 NS audrey.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0