Apex domains cannot have CNAME records.
Question and response
Question
dig prod.aws.kpn.com. NS
Answer
prod.aws.kpn.com. 5 NS ns-1982.awsdns-55.co.uk.
prod.aws.kpn.com. 5 NS ns-282.awsdns-35.com.
prod.aws.kpn.com. 5 NS ns-999.awsdns-60.net.
prod.aws.kpn.com. 5 NS ns-1254.awsdns-28.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0