Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-56.com. NS
Answer
awsdns-56.com. 5 NS g-ns-1208.awsdns-56.com.
awsdns-56.com. 5 NS g-ns-1784.awsdns-56.com.
awsdns-56.com. 5 NS g-ns-57.awsdns-56.com.
awsdns-56.com. 5 NS g-ns-632.awsdns-56.com.
Authority
The response has no authority records.
Additional
g-ns-57.awsdns-56.com. 5 A 205.251.192.57
g-ns-632.awsdns-56.com. 5 A 205.251.194.120
g-ns-1208.awsdns-56.com. 5 A 205.251.196.184
g-ns-1784.awsdns-56.com. 5 A 205.251.198.248
g-ns-57.awsdns-56.com. 5 AAAA 2600:9000:5300:3900:0:0:0:1
g-ns-632.awsdns-56.com. 5 AAAA 2600:9000:5302:7800:0:0:0:1
g-ns-1208.awsdns-56.com. 5 AAAA 2600:9000:5304:b800:0:0:0:1
g-ns-1784.awsdns-56.com. 5 AAAA 2600:9000:5306:f800:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0