Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-10.co.uk. NS
Answer
awsdns-10.co.uk. 5 NS g-ns-906.awsdns-10.co.uk.
awsdns-10.co.uk. 5 NS g-ns-1485.awsdns-10.co.uk.
awsdns-10.co.uk. 5 NS g-ns-1806.awsdns-10.co.uk.
awsdns-10.co.uk. 5 NS g-ns-330.awsdns-10.co.uk.
Authority
The response has no authority records.
Additional
g-ns-330.awsdns-10.co.uk. 5 A 205.251.193.74
g-ns-906.awsdns-10.co.uk. 5 A 205.251.195.138
g-ns-1485.awsdns-10.co.uk. 5 A 205.251.197.205
g-ns-1806.awsdns-10.co.uk. 5 A 205.251.199.14
g-ns-330.awsdns-10.co.uk. 5 AAAA 2600:9000:5301:4a00:0:0:0:1
g-ns-906.awsdns-10.co.uk. 5 AAAA 2600:9000:5303:8a00:0:0:0:1
g-ns-1485.awsdns-10.co.uk. 5 AAAA 2600:9000:5305:cd00:0:0:0:1
g-ns-1806.awsdns-10.co.uk. 5 AAAA 2600:9000:5307:e00:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0