Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-cn-42.com. NS
Answer
awsdns-cn-42.com. 3 NS g-ns-432.awsdns-cn-42.com.
awsdns-cn-42.com. 3 NS g-ns-1684.awsdns-cn-42.com.
awsdns-cn-42.com. 3 NS g-ns-intl-432.awsdns-cn-42.com.
awsdns-cn-42.com. 3 NS g-ns-3351.awsdns-cn-42.com.
awsdns-cn-42.com. 3 NS g-ns-2728.awsdns-cn-42.com.
awsdns-cn-42.com. 3 NS g-ns-intl-3351.awsdns-cn-42.com.
Authority
The response has no authority records.
Additional
g-ns-432.awsdns-cn-42.com. 3 A 52.82.177.176
g-ns-1684.awsdns-cn-42.com. 3 A 52.82.182.148
g-ns-2728.awsdns-cn-42.com. 3 A 54.222.34.168
g-ns-3351.awsdns-cn-42.com. 3 A 54.222.37.23
g-ns-intl-432.awsdns-cn-42.com. 3 A 52.46.185.176
g-ns-intl-3351.awsdns-cn-42.com. 3 A 52.46.181.23
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0