Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-47.co.uk. NS
Answer
awsdns-47.co.uk. 5 NS g-ns-1522.awsdns-47.co.uk.
awsdns-47.co.uk. 5 NS g-ns-943.awsdns-47.co.uk.
awsdns-47.co.uk. 5 NS g-ns-367.awsdns-47.co.uk.
awsdns-47.co.uk. 5 NS g-ns-1843.awsdns-47.co.uk.
Authority
The response has no authority records.
Additional
g-ns-367.awsdns-47.co.uk. 5 A 205.251.193.111
g-ns-943.awsdns-47.co.uk. 5 A 205.251.195.175
g-ns-1522.awsdns-47.co.uk. 5 A 205.251.197.242
g-ns-1843.awsdns-47.co.uk. 5 A 205.251.199.51
g-ns-367.awsdns-47.co.uk. 5 AAAA 2600:9000:5301:6f00:0:0:0:1
g-ns-943.awsdns-47.co.uk. 5 AAAA 2600:9000:5303:af00:0:0:0:1
g-ns-1522.awsdns-47.co.uk. 5 AAAA 2600:9000:5305:f200:0:0:0:1
g-ns-1843.awsdns-47.co.uk. 5 AAAA 2600:9000:5307:3300:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0