Bring a large pot of water to a boil. Add the spaghetti and cook according to the package instructions. Once done, drain the pasta, reserving some of the pasta water for later use in the sauce. Set the cooked pasta aside.
Heat olive oil in a large pan over medium heat. Add the chopped onion and sauté for about 6 minutes, or until the onion becomes soft and translucent.
For the full step-by-step instructions and video tutorial, download the Little Lunches app.