Apex domains cannot have CNAME records.
Question and response
Question
dig bcube.co.uk. NS
Answer
bcube.co.uk. 5 NS ns-886.awsdns-46.net.
bcube.co.uk. 5 NS ns-1304.awsdns-35.org.
bcube.co.uk. 5 NS ns-2025.awsdns-61.co.uk.
bcube.co.uk. 5 NS ns-420.awsdns-52.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0