Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-34.co.uk. NS
Answer
awsdns-34.co.uk. 5 NS g-ns-1830.awsdns-34.co.uk.
awsdns-34.co.uk. 5 NS g-ns-930.awsdns-34.co.uk.
awsdns-34.co.uk. 5 NS g-ns-354.awsdns-34.co.uk.
awsdns-34.co.uk. 5 NS g-ns-1509.awsdns-34.co.uk.
Authority
The response has no authority records.
Additional
g-ns-354.awsdns-34.co.uk. 5 A 205.251.193.98
g-ns-930.awsdns-34.co.uk. 5 A 205.251.195.162
g-ns-1509.awsdns-34.co.uk. 5 A 205.251.197.229
g-ns-1830.awsdns-34.co.uk. 5 A 205.251.199.38
g-ns-354.awsdns-34.co.uk. 5 AAAA 2600:9000:5301:6200:0:0:0:1
g-ns-930.awsdns-34.co.uk. 5 AAAA 2600:9000:5303:a200:0:0:0:1
g-ns-1509.awsdns-34.co.uk. 5 AAAA 2600:9000:5305:e500:0:0:0:1
g-ns-1830.awsdns-34.co.uk. 5 AAAA 2600:9000:5307:2600:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0