Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-02.co.uk. NS
Answer
awsdns-02.co.uk. 5 NS g-ns-1798.awsdns-02.co.uk.
awsdns-02.co.uk. 5 NS g-ns-898.awsdns-02.co.uk.
awsdns-02.co.uk. 5 NS g-ns-322.awsdns-02.co.uk.
awsdns-02.co.uk. 5 NS g-ns-1477.awsdns-02.co.uk.
Authority
The response has no authority records.
Additional
g-ns-322.awsdns-02.co.uk. 5 A 205.251.193.66
g-ns-898.awsdns-02.co.uk. 5 A 205.251.195.130
g-ns-1477.awsdns-02.co.uk. 5 A 205.251.197.197
g-ns-1798.awsdns-02.co.uk. 5 A 205.251.199.6
g-ns-322.awsdns-02.co.uk. 5 AAAA 2600:9000:5301:4200:0:0:0:1
g-ns-898.awsdns-02.co.uk. 5 AAAA 2600:9000:5303:8200:0:0:0:1
g-ns-1477.awsdns-02.co.uk. 5 AAAA 2600:9000:5305:c500:0:0:0:1
g-ns-1798.awsdns-02.co.uk. 5 AAAA 2600:9000:5307:600:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0