Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-cn-55.com. NS
Answer
awsdns-cn-55.com. 4 NS g-ns-2146.awsdns-cn-55.com.
awsdns-cn-55.com. 4 NS g-ns-833.awsdns-cn-55.com.
awsdns-cn-55.com. 4 NS g-ns-1462.awsdns-cn-55.com.
awsdns-cn-55.com. 4 NS g-ns-intl-3968.awsdns-cn-55.com.
awsdns-cn-55.com. 4 NS g-ns-intl-833.awsdns-cn-55.com.
awsdns-cn-55.com. 4 NS g-ns-3968.awsdns-cn-55.com.
Authority
The response has no authority records.
Additional
g-ns-833.awsdns-cn-55.com. 4 A 52.82.179.65
g-ns-1462.awsdns-cn-55.com. 4 A 52.82.181.182
g-ns-2146.awsdns-cn-55.com. 4 A 54.222.32.98
g-ns-3968.awsdns-cn-55.com. 4 A 54.222.39.128
g-ns-intl-833.awsdns-cn-55.com. 4 A 52.46.187.65
g-ns-intl-3968.awsdns-cn-55.com. 4 A 52.46.183.128
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0