Apex domains cannot have CNAME records.
Question and response
Question
dig bsgbmzkfwj.acm-validations.aws. NS
Answer
bsgbmzkfwj.acm-validations.aws. 5 NS ns-410.awsdns-51.com.
bsgbmzkfwj.acm-validations.aws. 5 NS ns-2007.awsdns-58.co.uk.
bsgbmzkfwj.acm-validations.aws. 5 NS ns-1172.awsdns-18.org.
bsgbmzkfwj.acm-validations.aws. 5 NS ns-978.awsdns-58.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0