Apex domains cannot have CNAME records.
Question and response
Question
dig plexus.edu.do. NS
Answer
plexus.edu.do. 5 NS ns10.wixdns.net.
plexus.edu.do. 5 NS ns11.wixdns.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0