Apex domains cannot have CNAME records.
Question and response
Question
dig cloudfiltering.com. NS
Answer
cloudfiltering.com. 4 NS ns-1851.awsdns-39.co.uk.
cloudfiltering.com. 4 NS ns-381.awsdns-47.com.
cloudfiltering.com. 4 NS ns-765.awsdns-31.net.
cloudfiltering.com. 4 NS ns-1258.awsdns-29.org.
Authority
The response has no authority records.
Additional
ns-765.awsdns-31.net. 2 A 205.251.194.253
ns-1258.awsdns-29.org. 2 A 205.251.196.234
ns-1851.awsdns-39.co.uk. 2 A 205.251.199.59
ns-381.awsdns-47.com. 2 AAAA 2600:9000:5301:7d00:0:0:0:1
ns-765.awsdns-31.net. 2 AAAA 2600:9000:5302:fd00:0:0:0:1
ns-1258.awsdns-29.org. 2 AAAA 2600:9000:5304:ea00:0:0:0:1
ns-1851.awsdns-39.co.uk. 2 AAAA 2600:9000:5307:3b00:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0