Apex domains cannot have CNAME records.
Question and response
Question
dig ca-west-1.compute.amazonaws.com. NS
Answer
ca-west-1.compute.amazonaws.com. 5 NS ns-1612.awsdns-09.co.uk.
ca-west-1.compute.amazonaws.com. 5 NS ns-1312.awsdns-36.org.
ca-west-1.compute.amazonaws.com. 5 NS ns-18.awsdns-02.com.
ca-west-1.compute.amazonaws.com. 5 NS ns-837.awsdns-40.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0