Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-06.co.uk. NS
Answer
awsdns-06.co.uk. 5 NS g-ns-1802.awsdns-06.co.uk.
awsdns-06.co.uk. 5 NS g-ns-326.awsdns-06.co.uk.
awsdns-06.co.uk. 5 NS g-ns-902.awsdns-06.co.uk.
awsdns-06.co.uk. 5 NS g-ns-1481.awsdns-06.co.uk.
Authority
The response has no authority records.
Additional
g-ns-326.awsdns-06.co.uk. 5 A 205.251.193.70
g-ns-902.awsdns-06.co.uk. 5 A 205.251.195.134
g-ns-1481.awsdns-06.co.uk. 5 A 205.251.197.201
g-ns-1802.awsdns-06.co.uk. 5 A 205.251.199.10
g-ns-326.awsdns-06.co.uk. 5 AAAA 2600:9000:5301:4600:0:0:0:1
g-ns-902.awsdns-06.co.uk. 5 AAAA 2600:9000:5303:8600:0:0:0:1
g-ns-1481.awsdns-06.co.uk. 5 AAAA 2600:9000:5305:c900:0:0:0:1
g-ns-1802.awsdns-06.co.uk. 5 AAAA 2600:9000:5307:a00:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0