Apex domains cannot have CNAME records.
Question and response
Question
dig ptg.net.do. NS
Answer
ptg.net.do. 5 NS mns01.domaincontrol.com.
ptg.net.do. 5 NS mns02.domaincontrol.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0