Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-46.co.uk. NS
Answer
awsdns-46.co.uk. 5 NS g-ns-942.awsdns-46.co.uk.
awsdns-46.co.uk. 5 NS g-ns-366.awsdns-46.co.uk.
awsdns-46.co.uk. 5 NS g-ns-1842.awsdns-46.co.uk.
awsdns-46.co.uk. 5 NS g-ns-1521.awsdns-46.co.uk.
Authority
The response has no authority records.
Additional
g-ns-366.awsdns-46.co.uk. 5 A 205.251.193.110
g-ns-942.awsdns-46.co.uk. 5 A 205.251.195.174
g-ns-1521.awsdns-46.co.uk. 5 A 205.251.197.241
g-ns-1842.awsdns-46.co.uk. 5 A 205.251.199.50
g-ns-366.awsdns-46.co.uk. 5 AAAA 2600:9000:5301:6e00:0:0:0:1
g-ns-942.awsdns-46.co.uk. 5 AAAA 2600:9000:5303:ae00:0:0:0:1
g-ns-1521.awsdns-46.co.uk. 5 AAAA 2600:9000:5305:f100:0:0:0:1
g-ns-1842.awsdns-46.co.uk. 5 AAAA 2600:9000:5307:3200:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0