When you register a domain with your cdmon user, by default the servers assigned to the new domain are the ones from cdmon. 

From your cdmon control panel, you can modify the default DNS server so that when you register a new domain, it is automatically assigned the desired DNS server. 

How to modify the default DNS

Once you access your cdmon control panel, you just need to go to User management and click on Default DNS:

Next, it will show whether the option is enabled or disabled. By default, it will be enabled with the cdmon DNS servers.

Here you must replace the name of our DNS servers with the name of the server you want to be set by default when registering a domain.

Once you have made the change, simply click on Save data for it to be applied: