Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-49.co.uk. NS
Answer
awsdns-49.co.uk. 5 NS g-ns-1845.awsdns-49.co.uk.
awsdns-49.co.uk. 5 NS g-ns-945.awsdns-49.co.uk.
awsdns-49.co.uk. 5 NS g-ns-369.awsdns-49.co.uk.
awsdns-49.co.uk. 5 NS g-ns-1524.awsdns-49.co.uk.
Authority
The response has no authority records.
Additional
g-ns-369.awsdns-49.co.uk. 5 A 205.251.193.113
g-ns-945.awsdns-49.co.uk. 5 A 205.251.195.177
g-ns-1524.awsdns-49.co.uk. 5 A 205.251.197.244
g-ns-1845.awsdns-49.co.uk. 5 A 205.251.199.53
g-ns-369.awsdns-49.co.uk. 5 AAAA 2600:9000:5301:7100:0:0:0:1
g-ns-945.awsdns-49.co.uk. 5 AAAA 2600:9000:5303:b100:0:0:0:1
g-ns-1524.awsdns-49.co.uk. 5 AAAA 2600:9000:5305:f400:0:0:0:1
g-ns-1845.awsdns-49.co.uk. 5 AAAA 2600:9000:5307:3500:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0