Apex domains cannot have CNAME records.
Question and response
Question
dig uxapp.io. NS
Answer
uxapp.io. 5 NS pns31.cloudns.net.
uxapp.io. 5 NS pns32.cloudns.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0