Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-31.com. NS
Answer
awsdns-31.com. 5 NS g-ns-1183.awsdns-31.com.
awsdns-31.com. 5 NS g-ns-607.awsdns-31.com.
awsdns-31.com. 5 NS g-ns-32.awsdns-31.com.
awsdns-31.com. 5 NS g-ns-1759.awsdns-31.com.
Authority
The response has no authority records.
Additional
g-ns-32.awsdns-31.com. 5 A 205.251.192.32
g-ns-607.awsdns-31.com. 5 A 205.251.194.95
g-ns-1183.awsdns-31.com. 5 A 205.251.196.159
g-ns-1759.awsdns-31.com. 5 A 205.251.198.223
g-ns-32.awsdns-31.com. 5 AAAA 2600:9000:5300:2000:0:0:0:1
g-ns-607.awsdns-31.com. 5 AAAA 2600:9000:5302:5f00:0:0:0:1
g-ns-1183.awsdns-31.com. 5 AAAA 2600:9000:5304:9f00:0:0:0:1
g-ns-1759.awsdns-31.com. 5 AAAA 2600:9000:5306:df00:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0