Apex domains cannot have CNAME records.
Question and response
Question
dig strath.ac.uk. NS
Answer
strath.ac.uk. 4 NS dns0.strath.ac.uk.
strath.ac.uk. 4 NS ns4.ja.net.
strath.ac.uk. 4 NS dns1.strath.ac.uk.
Authority
The response has no authority records.
Additional
ns4.ja.net. 4 A 193.62.157.66
dns0.strath.ac.uk. 4 A 130.159.248.11
dns1.strath.ac.uk. 4 A 130.159.248.9
ns4.ja.net. 4 AAAA 2001:630:0:47:0:0:0:42
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0