Apex domains cannot have CNAME records.
Question and response
Question
dig macau.ctm.net. NS
Answer
macau.ctm.net. 5 NS vassun1.macau.ctm.net.
macau.ctm.net. 5 NS ns3.macau.ctm.net.
macau.ctm.net. 5 NS vassun2.macau.ctm.net.
Authority
The response has no authority records.
Additional
ns3.macau.ctm.net. 5 A 202.175.36.8
vassun1.macau.ctm.net. 5 A 202.175.3.3
vassun2.macau.ctm.net. 5 A 202.175.3.8
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0