Apex domains cannot have CNAME records.
Question and response
Question
dig trustpilotmail.com. NS
Answer
trustpilotmail.com. 5 NS ns-1780.awsdns-30.co.uk.
trustpilotmail.com. 5 NS ns-672.awsdns-20.net.
trustpilotmail.com. 5 NS ns-423.awsdns-52.com.
trustpilotmail.com. 5 NS ns-1272.awsdns-31.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0