Apex domains cannot have CNAME records.
Question and response
Question
dig iomg.edu.do. NS
Answer
iomg.edu.do. 5 NS ns4179.dns.dyn.com.
iomg.edu.do. 5 NS ns2178.dns.dyn.com.
iomg.edu.do. 5 NS ns1148.dns.dyn.com.
iomg.edu.do. 5 NS ns3186.dns.dyn.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0