Example of how to register rendering module explicitly

app.rb

# app/app.rb
class Demo < Padrino::Application
  register Padrino::Rendering # <= Add this line
  # ...
  register Padrino::Helper
end

apps.rb

# config/apps.rb
Padrino.configure_apps do
  enable :sessions
  # $ padrino rake gen
  # $ rake secret
  set :session_secret, "long secret key pasted here" 
end

Or alternatively you can use different rendering modules, such as template inheritance rendering: http://blog.101ideas.cz/posts/padrino-and-template-inheritance.html