Apex domains cannot have CNAME records.
Question and response
Question
dig ca-central-1.amazonaws.com. NS
Answer
ca-central-1.amazonaws.com. 5 NS ns-1134.awsdns-13.org.
ca-central-1.amazonaws.com. 5 NS ns-710.awsdns-24.net.
ca-central-1.amazonaws.com. 5 NS ns-447.awsdns-55.com.
ca-central-1.amazonaws.com. 5 NS ns-1736.awsdns-25.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0