Apex domains cannot have CNAME records.
Question and response
Question
dig wpdns.com. NS
Answer
wpdns.com. 3 NS ns1.wpdns.com.
wpdns.com. 3 NS ns2.wpdns.com.
Authority
The response has no authority records.
Additional
ns1.wpdns.com. 3 A 103.215.136.98
ns2.wpdns.com. 3 A 103.215.136.213
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0