Apex domains cannot have CNAME records.
Question and response
Question
dig sn4.com. NS
Answer
sn4.com. 4 NS ns-64.awsdns-08.com.
sn4.com. 4 NS ns-1415.awsdns-48.org.
sn4.com. 4 NS ns-840.awsdns-41.net.
sn4.com. 4 NS ns-1764.awsdns-28.co.uk.
Authority
The response has no authority records.
Additional
ns-840.awsdns-41.net. 4 A 205.251.195.72
ns-1415.awsdns-48.org. 4 A 205.251.197.135
ns-1764.awsdns-28.co.uk. 4 A 205.251.198.228
ns-64.awsdns-08.com. 4 AAAA 2600:9000:5300:4000:0:0:0:1
ns-840.awsdns-41.net. 4 AAAA 2600:9000:5303:4800:0:0:0:1
ns-1415.awsdns-48.org. 4 AAAA 2600:9000:5305:8700:0:0:0:1
ns-1764.awsdns-28.co.uk. 4 AAAA 2600:9000:5306:e400:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0