For the meatballs: In a mixing bowl, add the ground beef, ricotta cheese, egg, sun-dried tomatoes, Parmigiano cheese, salt, and pepper. Mix well until the ingredients are evenly distributed. With your hands, shape the meatballs into the size of golf balls and then pat them down so they will evenly cook.
For the tomato sauce: In a large pot, heat the extra-virgin olive oil and cook the onions until translucent. Add the tomato puree and bring to a boil. Add the salt, and pepper, to taste and lower the heat to medium. Add the uncooked meatballs to the pot and let cook on medium heat for 30 minutes.