Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-14.co.uk. NS
Answer
awsdns-14.co.uk. 4 NS g-ns-334.awsdns-14.co.uk.
awsdns-14.co.uk. 4 NS g-ns-1810.awsdns-14.co.uk.
awsdns-14.co.uk. 4 NS g-ns-1489.awsdns-14.co.uk.
awsdns-14.co.uk. 4 NS g-ns-910.awsdns-14.co.uk.
Authority
The response has no authority records.
Additional
g-ns-334.awsdns-14.co.uk. 4 A 205.251.193.78
g-ns-910.awsdns-14.co.uk. 4 A 205.251.195.142
g-ns-1489.awsdns-14.co.uk. 4 A 205.251.197.209
g-ns-1810.awsdns-14.co.uk. 4 A 205.251.199.18
g-ns-334.awsdns-14.co.uk. 4 AAAA 2600:9000:5301:4e00:0:0:0:1
g-ns-910.awsdns-14.co.uk. 4 AAAA 2600:9000:5303:8e00:0:0:0:1
g-ns-1489.awsdns-14.co.uk. 4 AAAA 2600:9000:5305:d100:0:0:0:1
g-ns-1810.awsdns-14.co.uk. 4 AAAA 2600:9000:5307:1200:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0