Apex domains cannot have CNAME records.
Question and response
Question
dig tangocard.com. NS
Answer
tangocard.com. 5 NS ns-1687.awsdns-18.co.uk.
tangocard.com. 5 NS ns-783.awsdns-33.net.
tangocard.com. 5 NS ns-209.awsdns-26.com.
tangocard.com. 5 NS ns-1250.awsdns-28.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0