Apex domains cannot have CNAME records.
Question and response
Question
dig awsdns-26.co.uk. NS
Answer
awsdns-26.co.uk. 1 NS g-ns-346.awsdns-26.co.uk.
awsdns-26.co.uk. 1 NS g-ns-1822.awsdns-26.co.uk.
awsdns-26.co.uk. 1 NS g-ns-1501.awsdns-26.co.uk.
awsdns-26.co.uk. 1 NS g-ns-922.awsdns-26.co.uk.
Authority
The response has no authority records.
Additional
g-ns-346.awsdns-26.co.uk. 1 A 205.251.193.90
g-ns-922.awsdns-26.co.uk. 1 A 205.251.195.154
g-ns-1501.awsdns-26.co.uk. 1 A 205.251.197.221
g-ns-1822.awsdns-26.co.uk. 1 A 205.251.199.30
g-ns-346.awsdns-26.co.uk. 1 AAAA 2600:9000:5301:5a00:0:0:0:1
g-ns-922.awsdns-26.co.uk. 1 AAAA 2600:9000:5303:9a00:0:0:0:1
g-ns-1501.awsdns-26.co.uk. 1 AAAA 2600:9000:5305:dd00:0:0:0:1
g-ns-1822.awsdns-26.co.uk. 1 AAAA 2600:9000:5307:1e00:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0