Ricotta Stuffed Meatballs

Name: Ricotta Stuffed Meatballs
Ingredients: Making the Meatballs; 1/2 cup yellow onions (about 1/2 of a medium size onion), finely chopped; 1/2 tablespoon extra virgin olive oil; 3 cloves garlic, finely chopped; 2 slices rustic bread (stale is fine); 1 cup milk; 12 ounces bulk Italian sausage (spicy if you like extra heat; otherwise mild is fine); 12 ounces good-quality ground beef; 2 large eggs, beaten; 3 tablespoons fresh parsley, finely chopped; 1/2 cup Parmigiano Reggiano cheese, grated; 3/4 cup fresh homemade ricotta (preferably not from the supermarket); 1/8 cup fresh parsley, chopped; 2 tablespoons fresh basil, chopped; 1/2 cup pine nuts, toasted; 1 teaspoon salt (or more to taste), divided; Freshly ground black pepper, to taste; 1/2 cup dry bread crumbs (if needed); Making the Marinara Sauce; 1 small yellow onion, chopped; 2 tablespoons extra virgin olive oil; 4 cloves garlic, finely chopped; 1 28 ounce can of good quality tomatoes, preferably San Marzano (if it's tomato season, use vine ripened tomatoes -- peel and seed them first); Salt and freshly ground black pepper to taste; 3 tablespoons fresh parsley, chopped; 3 tablespoons fresh basil, chopped