Apex domains cannot have CNAME records.
Question and response
Question
dig s17.wpxhosting.com. NS
Answer
s17.wpxhosting.com. 5 NS ns40.wpxhosting.com.
s17.wpxhosting.com. 5 NS ns41.wpxhosting.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0