This casserole is simple and delicious, and makes a perfect snack during a picnic (bento anyone?)—you should use it as a basic idea for a casserole, since the pasta sauce is the stable and the most important piece of the meal. It's also a very tweak-able recipe! :-)
When you make your own pasta, you will always end up with some scraps, even more if you make ravioli. You can easily recycle this leftover pasta to make maltagliati, meaning "poorly cut" in Italian, which was traditionally meant as food for the poor. We are way past that, and today you can enjoy rich texture and amazing flavor of your pasta without the social stigma ;-)
Tuna paste is ridiculously easy to prepare and makes a great no cooking bento, cutting the preparation time to less than 20 minutes, including rice cooking time! Now, that's what I would call cooking on the go! You can also use the tuna paste for a great tasting onigiri or sushi.