Apex domains cannot have CNAME records.
Question and response
Question
dig jkddzztszm.acm-validations.aws. NS
Answer
jkddzztszm.acm-validations.aws. 5 NS ns-1337.awsdns-39.org.
jkddzztszm.acm-validations.aws. 5 NS ns-653.awsdns-17.net.
jkddzztszm.acm-validations.aws. 5 NS ns-266.awsdns-33.com.
jkddzztszm.acm-validations.aws. 5 NS ns-1701.awsdns-20.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0