Apex domains cannot have CNAME records.
Question and response
Question
dig sigasfl.gov.do. NS
Answer
sigasfl.gov.do. 5 NS ns1.napdelcaribe.com.do.
sigasfl.gov.do. 5 NS ns2.napdelcaribe.com.do.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0