Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-11.co.uk. NS
Answer
awsdns-11.co.uk. 5 NS g-ns-1486.awsdns-11.co.uk.
awsdns-11.co.uk. 5 NS g-ns-1807.awsdns-11.co.uk.
awsdns-11.co.uk. 5 NS g-ns-331.awsdns-11.co.uk.
awsdns-11.co.uk. 5 NS g-ns-907.awsdns-11.co.uk.
Authority
The response has no authority records.
Additional
g-ns-331.awsdns-11.co.uk. 5 A 205.251.193.75
g-ns-907.awsdns-11.co.uk. 5 A 205.251.195.139
g-ns-1486.awsdns-11.co.uk. 5 A 205.251.197.206
g-ns-1807.awsdns-11.co.uk. 5 A 205.251.199.15
g-ns-331.awsdns-11.co.uk. 5 AAAA 2600:9000:5301:4b00:0:0:0:1
g-ns-907.awsdns-11.co.uk. 5 AAAA 2600:9000:5303:8b00:0:0:0:1
g-ns-1486.awsdns-11.co.uk. 5 AAAA 2600:9000:5305:ce00:0:0:0:1
g-ns-1807.awsdns-11.co.uk. 5 AAAA 2600:9000:5307:f00:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0