Apex domains cannot have CNAME records.
Question and response
Question
dig ses.edu.do. NS
Answer
ses.edu.do. 4 NS cdns1.main-hosting.eu.
ses.edu.do. 4 NS cdns2.main-hosting.eu.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0