Apex domains cannot have CNAME records.
Question and response
Question
dig ap-northeast-2.compute.amazonaws.com. NS
Answer
ap-northeast-2.compute.amazonaws.com. 5 NS ns-555.awsdns-05.net.
ap-northeast-2.compute.amazonaws.com. 5 NS ns-271.awsdns-33.com.
ap-northeast-2.compute.amazonaws.com. 5 NS ns-1657.awsdns-15.co.uk.
ap-northeast-2.compute.amazonaws.com. 5 NS ns-1386.awsdns-45.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0