Apex domains cannot have CNAME records.
Question and response
Question
dig sendoso.com. NS
Answer
sendoso.com. 5 NS ns-2036.awsdns-62.co.uk.
sendoso.com. 5 NS ns-558.awsdns-05.net.
sendoso.com. 5 NS ns-239.awsdns-29.com.
sendoso.com. 5 NS ns-1316.awsdns-36.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0