Apex domains cannot have CNAME records.
Question and response
Question
dig sgnic.sg. NS
Answer
sgnic.sg. 2 NS dsany3.sgnic.sg.
sgnic.sg. 2 NS dsany4.sgnic.sg.
sgnic.sg. 2 NS dsany2.sgnic.sg.
Authority
The response has no authority records.
Additional
dsany2.sgnic.sg. 169726 A 185.159.197.170
dsany3.sgnic.sg. 169726 A 185.159.198.170
dsany4.sgnic.sg. 169726 A 45.142.220.65
dsany2.sgnic.sg. 169726 AAAA 2620:10a:80aa:0:0:0:0:170
dsany3.sgnic.sg. 169726 AAAA 2620:10a:80ab:0:0:0:0:170
dsany4.sgnic.sg. 169726 AAAA 2a0e:dbc0:1:0:0:0:0:65
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0