Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-20.net. NS
Answer
awsdns-20.net. 5 NS g-ns-1940.awsdns-20.net.
awsdns-20.net. 5 NS g-ns-1364.awsdns-20.net.
awsdns-20.net. 5 NS g-ns-469.awsdns-20.net.
awsdns-20.net. 5 NS g-ns-790.awsdns-20.net.
Authority
The response has no authority records.
Additional
g-ns-469.awsdns-20.net. 5 A 205.251.193.213
g-ns-790.awsdns-20.net. 5 A 205.251.195.22
g-ns-1364.awsdns-20.net. 5 A 205.251.197.84
g-ns-1940.awsdns-20.net. 5 A 205.251.199.148
g-ns-469.awsdns-20.net. 5 AAAA 2600:9000:5301:d500:0:0:0:1
g-ns-790.awsdns-20.net. 5 AAAA 2600:9000:5303:1600:0:0:0:1
g-ns-1364.awsdns-20.net. 5 AAAA 2600:9000:5305:5400:0:0:0:1
g-ns-1940.awsdns-20.net. 5 AAAA 2600:9000:5307:9400:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0