[Rails3] How to send Content-type HTTP header in all my html files generated by Rails3

I wish to replicate this:

<?php header('Content-type: text/html; charset=utf-8'); ?>

with Rails 3 in each and every view I got. I guess I should look at
application.html.erb to add something.
Not only for avoiding this bug:

but also it makes sense to send the html files generated by my views
with such header.
Can you help me please?
Thanks a lot.