Apex domains cannot have CNAME records.
Question and response
Question
dig dip31.dutaint.com. NS
Answer
dip31.dutaint.com. 5 NS ns1.dutaint.com.
dip31.dutaint.com. 5 NS ns3.dutaint.com.
dip31.dutaint.com. 5 NS ns2.dutaint.com.
Authority
The response has no authority records.
Additional
ns1.dutaint.com. 5 A 103.242.180.166
ns2.dutaint.com. 5 A 113.20.31.186
ns3.dutaint.com. 5 A 113.20.31.196
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0