Apex domains cannot have CNAME records.
Question and response
Question
dig dotplex.host. NS
Answer
dotplex.host. 5 NS ns.dotplex.net.
dotplex.host. 5 NS ns3.dotplex.ie.
dotplex.host. 5 NS ns2.dotplex.de.
Authority
The response has no authority records.
Additional
ns.dotplex.net. 5 A 185.231.124.53
ns2.dotplex.de. 5 A 82.165.42.81
ns3.dotplex.ie. 5 A 116.202.81.237
ns.dotplex.net. 5 AAAA 2a0c:5f00:1:135:0:0:0:0
ns2.dotplex.de. 5 AAAA 2a01:239:0:89:0:0:0:1
ns3.dotplex.ie. 5 AAAA 2a01:4f8:231:398f:3:0:0:0
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0