Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-39.com. NS
Answer
awsdns-39.com. 5 NS g-ns-1767.awsdns-39.com.
awsdns-39.com. 5 NS g-ns-1191.awsdns-39.com.
awsdns-39.com. 5 NS g-ns-40.awsdns-39.com.
awsdns-39.com. 5 NS g-ns-615.awsdns-39.com.
Authority
The response has no authority records.
Additional
g-ns-40.awsdns-39.com. 5 A 205.251.192.40
g-ns-615.awsdns-39.com. 5 A 205.251.194.103
g-ns-1191.awsdns-39.com. 5 A 205.251.196.167
g-ns-1767.awsdns-39.com. 5 A 205.251.198.231
g-ns-40.awsdns-39.com. 5 AAAA 2600:9000:5300:2800:0:0:0:1
g-ns-615.awsdns-39.com. 5 AAAA 2600:9000:5302:6700:0:0:0:1
g-ns-1191.awsdns-39.com. 5 AAAA 2600:9000:5304:a700:0:0:0:1
g-ns-1767.awsdns-39.com. 5 AAAA 2600:9000:5306:e700:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0