Apex domains cannot have CNAME records.
Question and response
Question
dig amzndns.net. NS
Answer
amzndns.net. 5 NS g-ns2.amzndns.net.
amzndns.net. 5 NS g-ns3.amzndns.net.
amzndns.net. 5 NS g-ns4.amzndns.net.
amzndns.net. 5 NS g-ns1.amzndns.net.
Authority
The response has no authority records.
Additional
g-ns1.amzndns.net. 5 A 205.251.196.229
g-ns2.amzndns.net. 5 A 205.251.193.135
g-ns3.amzndns.net. 5 A 205.251.194.146
g-ns4.amzndns.net. 5 A 205.251.198.211
g-ns1.amzndns.net. 5 AAAA 2600:9000:5304:e500:0:0:0:1
g-ns2.amzndns.net. 5 AAAA 2600:9000:5301:8700:0:0:0:1
g-ns3.amzndns.net. 5 AAAA 2600:9000:5302:9200:0:0:0:1
g-ns4.amzndns.net. 5 AAAA 2600:9000:5306:d300:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0