Apex domains cannot have CNAME records.
Question and response
Question
dig cymbaltageneric30.com. NS
Answer
cymbaltageneric30.com. 5 NS ns-623.awsdns-13.net.
cymbaltageneric30.com. 5 NS ns-2025.awsdns-61.co.uk.
cymbaltageneric30.com. 5 NS ns-539.awsdns-03.net.
cymbaltageneric30.com. 5 NS ns-1324.awsdns-37.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0