Apex domains cannot have CNAME records.
Question and response
Question
dig tra.gov.om. NS
Answer
tra.gov.om. 5 NS ns3.ict.omantel.om.
tra.gov.om. 5 NS ns4.ict.omantel.om.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0