Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-31.net. NS
Answer
awsdns-31.net. 5 NS g-ns-1951.awsdns-31.net.
awsdns-31.net. 5 NS g-ns-480.awsdns-31.net.
awsdns-31.net. 5 NS g-ns-801.awsdns-31.net.
awsdns-31.net. 5 NS g-ns-1375.awsdns-31.net.
Authority
The response has no authority records.
Additional
g-ns-480.awsdns-31.net. 5 A 205.251.193.224
g-ns-801.awsdns-31.net. 5 A 205.251.195.33
g-ns-1375.awsdns-31.net. 5 A 205.251.197.95
g-ns-1951.awsdns-31.net. 5 A 205.251.199.159
g-ns-480.awsdns-31.net. 5 AAAA 2600:9000:5301:e000:0:0:0:1
g-ns-801.awsdns-31.net. 5 AAAA 2600:9000:5303:2100:0:0:0:1
g-ns-1375.awsdns-31.net. 5 AAAA 2600:9000:5305:5f00:0:0:0:1
g-ns-1951.awsdns-31.net. 5 AAAA 2600:9000:5307:9f00:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0