Apex domains cannot have CNAME records.
Question and response
Question
dig heatherglasgow.com. NS
Answer
heatherglasgow.com. 5 NS ns-1914.awsdns-47.co.uk.
heatherglasgow.com. 5 NS ns-836.awsdns-40.net.
heatherglasgow.com. 5 NS ns-904.awsdns-49.net.
heatherglasgow.com. 5 NS ns-2004.awsdns-58.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0