Apex domains cannot have CNAME records.
Question and response
Question
dig katapult.io. NS
Answer
katapult.io. 5 NS ns1.krystal.co.uk.
katapult.io. 5 NS ns2.krystal.co.uk.
Authority
The response has no authority records.
Additional
ns1.krystal.co.uk. 5 A 77.72.0.11
ns2.krystal.co.uk. 5 A 139.162.230.184
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0