Apex domains cannot have CNAME records.
Question and response
Question
dig fra1.prodgdc.com. NS
Answer
fra1.prodgdc.com. 5 NS ns-1186.awsdns-20.org.
fra1.prodgdc.com. 5 NS ns-994.awsdns-60.net.
fra1.prodgdc.com. 5 NS ns-259.awsdns-32.com.
fra1.prodgdc.com. 5 NS ns-1886.awsdns-43.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0