I don't think one size fits all here. To me, a good tutorial app is one that effectively showcases the strengths of a framework while being honest about weaknes

I don't think one size fits all here. To me, a good tutorial app is one that effectively showcases the strengths of a framework while being honest about weaknesses. So for Django/Rails, anything that goes over CRUD operations would be good. For Flask/Sinatra, an API endpoint. For Meteor, a small, realtime chat application. You get the idea. And keep it simple. Don't try to cram everything into a tutorial — especially if there is a lot of complicated setup required. Just give me the lay of the land and at the end of the tutorial a link to the reference docs so I can keep going if I want.