Heat the olive oil in a pot over medium heat. Add the onions, some sea salt, and black pepper and cook until soft, about 5 minutes. Add the garlic and cook for another minute or two. Next, add the grated carrot and parsley. Stir and cook until the carrot is soft, about 5 minutes. Add the canned tomatoes and all of their juices. Bring to a boil, stir, and reduce the heat to a simmer. Cook until the sauce is thickened, stirring occasionally, about 30 minutes.
Set a food mill over a large mixing bowl. Slowly add the sauce to the food mill, working it through carefully. The food mill will provide the best texture for the sauce. If you do not have a food mill, you can also puree the sauce in a food processor but try to leave a little bit of texture. Season with sea salt and black pepper.
Cook your pasta until al dente. Toss the pasta with the sauce to coat. Finish with Parmigiano Reggiano if you like.