Accessing json response from the server in Ember

I have an Ember CLI app with Rails as backend API. At some point I perform an action (a model.save() in this case) and want to get a custom json response from the server to access it from my Ember app. I'm getting the response I want, I'm just not sure how to handle it in Ember, how to gain access to the object and its properties. I know I can use .then() and put something between those parentheses, but this will be ember's response with the saved object, not the json I get as a response from the backend.