Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-40.org. NS
Answer
awsdns-40.org. 5 NS g-ns-1640.awsdns-40.org.
awsdns-40.org. 5 NS g-ns-746.awsdns-40.org.
awsdns-40.org. 5 NS g-ns-168.awsdns-40.org.
awsdns-40.org. 5 NS g-ns-1067.awsdns-40.org.
Authority
The response has no authority records.
Additional
g-ns-168.awsdns-40.org. 5 A 205.251.192.168
g-ns-746.awsdns-40.org. 5 A 205.251.194.234
g-ns-1067.awsdns-40.org. 5 A 205.251.196.43
g-ns-1640.awsdns-40.org. 5 A 205.251.198.104
g-ns-168.awsdns-40.org. 5 AAAA 2600:9000:5300:a800:0:0:0:1
g-ns-746.awsdns-40.org. 5 AAAA 2600:9000:5302:ea00:0:0:0:1
g-ns-1067.awsdns-40.org. 5 AAAA 2600:9000:5304:2b00:0:0:0:1
g-ns-1640.awsdns-40.org. 5 AAAA 2600:9000:5306:6800:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0