Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-07.co.uk. NS
Answer
awsdns-07.co.uk. 5 NS g-ns-1803.awsdns-07.co.uk.
awsdns-07.co.uk. 5 NS g-ns-1482.awsdns-07.co.uk.
awsdns-07.co.uk. 5 NS g-ns-327.awsdns-07.co.uk.
awsdns-07.co.uk. 5 NS g-ns-903.awsdns-07.co.uk.
Authority
The response has no authority records.
Additional
g-ns-327.awsdns-07.co.uk. 5 A 205.251.193.71
g-ns-903.awsdns-07.co.uk. 5 A 205.251.195.135
g-ns-1482.awsdns-07.co.uk. 5 A 205.251.197.202
g-ns-1803.awsdns-07.co.uk. 5 A 205.251.199.11
g-ns-327.awsdns-07.co.uk. 5 AAAA 2600:9000:5301:4700:0:0:0:1
g-ns-903.awsdns-07.co.uk. 5 AAAA 2600:9000:5303:8700:0:0:0:1
g-ns-1482.awsdns-07.co.uk. 5 AAAA 2600:9000:5305:ca00:0:0:0:1
g-ns-1803.awsdns-07.co.uk. 5 AAAA 2600:9000:5307:b00:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0