Apex domains cannot have CNAME records.
Question and response
Question
dig muasamthongminh24h.com. NS
Answer
muasamthongminh24h.com. 5 NS ns-479.awsdns-59.com.
muasamthongminh24h.com. 5 NS ns-1615.awsdns-09.co.uk.
muasamthongminh24h.com. 5 NS ns-1439.awsdns-51.org.
muasamthongminh24h.com. 5 NS ns-760.awsdns-31.net.
Authority
The response has no authority records.
Additional
ns-479.awsdns-59.com. 1 A 205.251.193.223
ns-479.awsdns-59.com. 1 AAAA 2600:9000:5301:df00:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0