Apex domains cannot have CNAME records.
Question and response
Question
dig titan.web.oficinadigital.do. NS
Answer
titan.web.oficinadigital.do. 5 NS titan2.oficinadigital.do.
titan.web.oficinadigital.do. 5 NS titan1.oficinadigital.do.
Authority
The response has no authority records.
Additional
titan1.oficinadigital.do. 5 A 135.148.120.134
titan2.oficinadigital.do. 5 A 135.148.120.134
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0