Apex domains cannot have CNAME records.
Question and response
Question
dig pucmm.edu.do. NS
Answer
pucmm.edu.do. 4 NS ns2.pucmm.edu.do.
pucmm.edu.do. 4 NS ns1.pucmm.edu.do.
Authority
The response has no authority records.
Additional
ns1.pucmm.edu.do. 4 A 190.113.65.11
ns2.pucmm.edu.do. 4 A 190.113.73.10
ns1.pucmm.edu.do. 4 AAAA 2001:13e0:0:1:0:0:0:11
ns2.pucmm.edu.do. 4 AAAA 2001:13e0:8000:1:0:0:0:10
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0