Apex domains cannot have CNAME records.
Question and response
Question
dig hkvuiqjoua.acm-validations.aws. NS
Answer
hkvuiqjoua.acm-validations.aws. 5 NS ns-1501.awsdns-59.org.
hkvuiqjoua.acm-validations.aws. 5 NS ns-291.awsdns-36.com.
hkvuiqjoua.acm-validations.aws. 5 NS ns-764.awsdns-31.net.
hkvuiqjoua.acm-validations.aws. 5 NS ns-2003.awsdns-58.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0