Apex domains cannot have CNAME records.
Question and response
Question
dig aws.billingplatform.com. NS
Answer
aws.billingplatform.com. 1 NS ns-859.awsdns-43.net.
aws.billingplatform.com. 1 NS ns-1960.awsdns-53.co.uk.
aws.billingplatform.com. 1 NS ns-179.awsdns-22.com.
aws.billingplatform.com. 1 NS ns-1475.awsdns-56.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0