Machine to Machine between different tenants

Hi Auth0 team,

We have a use-case where we will be building a new feature common to all of our existing apps which lie on different Auth0 tenants and this feature will be needing an API call to a new application which will be built on a separate app:

Below is the gist of our architecture:

Untitled Diagram.drawio (2)

Given the above diagram - our existing apps (App1, 2 up to N) is already live and uses Auth0 for authentication and they are isolated between each other (e.g., App1 users has no access to App2 and vice-versa). We want it to keep it that way so now how do we go with our Portal features where it also has its own set of users which should not be able to login/access into App1 and so on.

We just want them to communicate via API calls (machine-to-machine for some data sharing action behind the scenes). So how or what will be your recommendations on this? Thanks!