Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-18.org. NS
Answer
awsdns-18.org. 5 NS g-ns-724.awsdns-18.org.
awsdns-18.org. 5 NS g-ns-1618.awsdns-18.org.
awsdns-18.org. 5 NS g-ns-146.awsdns-18.org.
awsdns-18.org. 5 NS g-ns-1045.awsdns-18.org.
Authority
The response has no authority records.
Additional
g-ns-146.awsdns-18.org. 5 A 205.251.192.146
g-ns-724.awsdns-18.org. 5 A 205.251.194.212
g-ns-1045.awsdns-18.org. 5 A 205.251.196.21
g-ns-1618.awsdns-18.org. 5 A 205.251.198.82
g-ns-146.awsdns-18.org. 5 AAAA 2600:9000:5300:9200:0:0:0:1
g-ns-724.awsdns-18.org. 5 AAAA 2600:9000:5302:d400:0:0:0:1
g-ns-1045.awsdns-18.org. 5 AAAA 2600:9000:5304:1500:0:0:0:1
g-ns-1618.awsdns-18.org. 5 AAAA 2600:9000:5306:5200:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0