Apex domains cannot have CNAME records.
Question and response
Question
dig coulsondomain.com. NS
Answer
coulsondomain.com. 5 NS ns-1141.awsdns-14.org.
coulsondomain.com. 5 NS ns-2040.awsdns-63.co.uk.
coulsondomain.com. 5 NS ns-289.awsdns-36.com.
coulsondomain.com. 5 NS ns-655.awsdns-17.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0