Apex domains cannot have CNAME records.
Question and response
Question
dig cudpx.com. NS
Answer
cudpx.com. 5 NS ns-1557.awsdns-02.co.uk.
cudpx.com. 5 NS ns-403.awsdns-50.com.
cudpx.com. 5 NS ns-740.awsdns-28.net.
cudpx.com. 5 NS ns-818.awsdns-38.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0