Apex domains cannot have CNAME records.
Question and response
Question
dig moh.gov.sg. NS
Answer
moh.gov.sg. 5 NS ns10.gdnsdef.com.
moh.gov.sg. 5 NS ns12.gdnsdef.com.
moh.gov.sg. 5 NS ns3.gdnsec.com.
moh.gov.sg. 5 NS a9-65.akam.net.
moh.gov.sg. 5 NS a3-67.akam.net.
moh.gov.sg. 5 NS a8-64.akam.net.
moh.gov.sg. 5 NS a1-6.akam.net.
moh.gov.sg. 5 NS ns12.gdnsec.com.
moh.gov.sg. 5 NS ns9.gdnsec.com.
moh.gov.sg. 5 NS ns7.gdnsdef.com.
moh.gov.sg. 5 NS a2-65.akam.net.
moh.gov.sg. 5 NS a20-66.akam.net.
Authority
The response has no authority records.
Additional
a9-65.akam.net. 4 A 184.85.248.65
a9-65.akam.net. 4 AAAA 2a02:26f0:117:0:0:0:0:41
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0