Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-54.co.uk. NS
Answer
awsdns-54.co.uk. 5 NS g-ns-1529.awsdns-54.co.uk.
awsdns-54.co.uk. 5 NS g-ns-950.awsdns-54.co.uk.
awsdns-54.co.uk. 5 NS g-ns-374.awsdns-54.co.uk.
awsdns-54.co.uk. 5 NS g-ns-1850.awsdns-54.co.uk.
Authority
The response has no authority records.
Additional
g-ns-374.awsdns-54.co.uk. 5 A 205.251.193.118
g-ns-950.awsdns-54.co.uk. 5 A 205.251.195.182
g-ns-1529.awsdns-54.co.uk. 5 A 205.251.197.249
g-ns-1850.awsdns-54.co.uk. 5 A 205.251.199.58
g-ns-374.awsdns-54.co.uk. 5 AAAA 2600:9000:5301:7600:0:0:0:1
g-ns-950.awsdns-54.co.uk. 5 AAAA 2600:9000:5303:b600:0:0:0:1
g-ns-1529.awsdns-54.co.uk. 5 AAAA 2600:9000:5305:f900:0:0:0:1
g-ns-1850.awsdns-54.co.uk. 5 AAAA 2600:9000:5307:3a00:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0