Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-20.org. NS
Answer
awsdns-20.org. 5 NS g-ns-148.awsdns-20.org.
awsdns-20.org. 5 NS g-ns-1047.awsdns-20.org.
awsdns-20.org. 5 NS g-ns-726.awsdns-20.org.
awsdns-20.org. 5 NS g-ns-1620.awsdns-20.org.
Authority
The response has no authority records.
Additional
g-ns-148.awsdns-20.org. 5 A 205.251.192.148
g-ns-726.awsdns-20.org. 5 A 205.251.194.214
g-ns-1047.awsdns-20.org. 5 A 205.251.196.23
g-ns-1620.awsdns-20.org. 5 A 205.251.198.84
g-ns-148.awsdns-20.org. 5 AAAA 2600:9000:5300:9400:0:0:0:1
g-ns-726.awsdns-20.org. 5 AAAA 2600:9000:5302:d600:0:0:0:1
g-ns-1047.awsdns-20.org. 5 AAAA 2600:9000:5304:1700:0:0:0:1
g-ns-1620.awsdns-20.org. 5 AAAA 2600:9000:5306:5400:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0