Apex domains cannot have CNAME records.
Question and response
Question
dig brilliant-group.co.uk. NS
Answer
brilliant-group.co.uk. 5 NS igor.ns.cloudflare.com.
brilliant-group.co.uk. 5 NS liv.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0