Apex domains cannot have CNAME records.
Question and response
Question
dig opetus.edu.do. NS
Answer
opetus.edu.do. 5 NS rocco.ns.cloudflare.com.
opetus.edu.do. 5 NS walk.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0