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! :-)
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.
Bento is not only rice, and you can eat a delicious meal with other ingredients like potatoes, green beans and... cornichons! This is my bento idea for days when I literally cannot look at rice, e.g. the day after sushi day. And, because most of the ingredients are pre-made in jars, you can quickly assemble this set when you're short on time. What's not to love about this bento idea?!