Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-63.com. NS
Answer
awsdns-63.com. 5 NS g-ns-639.awsdns-63.com.
awsdns-63.com. 5 NS g-ns-257.awsdns-63.com.
awsdns-63.com. 5 NS g-ns-1984.awsdns-63.com.
awsdns-63.com. 5 NS g-ns-1215.awsdns-63.com.
Authority
The response has no authority records.
Additional
g-ns-257.awsdns-63.com. 5 A 205.251.193.1
g-ns-639.awsdns-63.com. 5 A 205.251.194.127
g-ns-1215.awsdns-63.com. 5 A 205.251.196.191
g-ns-1984.awsdns-63.com. 5 A 205.251.199.192
g-ns-257.awsdns-63.com. 5 AAAA 2600:9000:5301:100:0:0:0:1
g-ns-639.awsdns-63.com. 5 AAAA 2600:9000:5302:7f00:0:0:0:1
g-ns-1215.awsdns-63.com. 5 AAAA 2600:9000:5304:bf00:0:0:0:1
g-ns-1984.awsdns-63.com. 5 AAAA 2600:9000:5307:c000:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0