Apex domains cannot have CNAME records.
Question and response
Question
dig cainhall.net. NS
Answer
cainhall.net. 5 NS ns-105.awsdns-13.com.
cainhall.net. 5 NS ns-97.awsdns-12.com.
cainhall.net. 5 NS ns-1160.awsdns-17.org.
cainhall.net. 5 NS ns-704.awsdns-24.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0