Apex domains cannot have CNAME records.
Question and response
Question
dig concentra.edu.do. NS
Answer
concentra.edu.do. 5 NS ns36.domaincontrol.com.
concentra.edu.do. 5 NS ns35.domaincontrol.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0