Apex domains cannot have CNAME records.
Question and response
Question
dig institutolexi.edu.do. NS
Answer
institutolexi.edu.do. 1 NS ns1.vm4371.tmdcloud.com.
institutolexi.edu.do. 1 NS ns2.vm4371.tmdcloud.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0