Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-cn-29.com. NS
Answer
awsdns-cn-29.com. 1 NS g-ns-1841.awsdns-cn-29.com.
awsdns-cn-29.com. 1 NS g-ns-2844.awsdns-cn-29.com.
awsdns-cn-29.com. 1 NS g-ns-intl-3159.awsdns-cn-29.com.
awsdns-cn-29.com. 1 NS g-ns-intl-985.awsdns-cn-29.com.
awsdns-cn-29.com. 1 NS g-ns-985.awsdns-cn-29.com.
awsdns-cn-29.com. 1 NS g-ns-3159.awsdns-cn-29.com.
Authority
The response has no authority records.
Additional
g-ns-985.awsdns-cn-29.com. 1 A 52.82.179.217
g-ns-1841.awsdns-cn-29.com. 1 A 52.82.183.49
g-ns-2844.awsdns-cn-29.com. 1 A 54.222.35.28
g-ns-3159.awsdns-cn-29.com. 1 A 54.222.36.87
g-ns-intl-985.awsdns-cn-29.com. 1 A 52.46.187.217
g-ns-intl-3159.awsdns-cn-29.com. 1 A 52.46.180.87
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0