Apex domains cannot have CNAME records.
Question and response
Question
dig zuora.com. NS
Answer
zuora.com. 5 NS ns-363.awsdns-45.com.
zuora.com. 5 NS ns-1376.awsdns-44.org.
zuora.com. 5 NS ns-713.awsdns-25.net.
zuora.com. 5 NS ns-1867.awsdns-41.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0