Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-63.co.uk. NS
Answer
awsdns-63.co.uk. 5 NS g-ns-959.awsdns-63.co.uk.
awsdns-63.co.uk. 5 NS g-ns-1219.awsdns-63.co.uk.
awsdns-63.co.uk. 5 NS g-ns-1540.awsdns-63.co.uk.
awsdns-63.co.uk. 5 NS g-ns-383.awsdns-63.co.uk.
Authority
The response has no authority records.
Additional
g-ns-383.awsdns-63.co.uk. 5 A 205.251.193.127
g-ns-959.awsdns-63.co.uk. 5 A 205.251.195.191
g-ns-1219.awsdns-63.co.uk. 5 A 205.251.196.195
g-ns-1540.awsdns-63.co.uk. 5 A 205.251.198.4
g-ns-383.awsdns-63.co.uk. 5 AAAA 2600:9000:5301:7f00:0:0:0:1
g-ns-959.awsdns-63.co.uk. 5 AAAA 2600:9000:5303:bf00:0:0:0:1
g-ns-1219.awsdns-63.co.uk. 5 AAAA 2600:9000:5304:c300:0:0:0:1
g-ns-1540.awsdns-63.co.uk. 5 AAAA 2600:9000:5306:400:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0