Apex domains cannot have CNAME records.
Question and response
Question
dig sendergen.com. NS
Answer
sendergen.com. 4 NS ns-154.awsdns-19.com.
sendergen.com. 4 NS ns-971.awsdns-57.net.
sendergen.com. 4 NS ns-1126.awsdns-12.org.
sendergen.com. 4 NS ns-1807.awsdns-33.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0