Apex domains cannot have CNAME records.
Question and response
Question
dig fluent.ltd.uk. NS
Answer
fluent.ltd.uk. 3 NS dns1.fluent.ltd.uk.
fluent.ltd.uk. 3 NS dns2.fluent.ltd.uk.
Authority
The response has no authority records.
Additional
dns1.fluent.ltd.uk. 3 A 195.78.94.253
dns2.fluent.ltd.uk. 3 A 195.78.94.254
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0