Yield: 8 servings.

3 tablespoons olive oil
3 medium white onions, chopped (about 3 cups)
3 (28-ounce) cans San Marzano whole peeled tomatoes
10 cloves garlic, minced
1 green bell pepper, cored and diced
1 cup dry red wine (cabernet sauvignon or merlot)
1 pound ground mild Italian sausage, cooked and drained
2 pounds ground sirloin, cooked and drained
3 tablespoons dried oregano
2 tablespoons dried basil
3 bay leaves
1 cup grated Parmesan cheese, plus more for serving
½ cup Italian parsley, chopped
3 tablespoons balsamic vinegar
1 teaspoon granulated sugar
1 teaspoon Kosher salt
½ teaspoon red chili flakes
3 tablespoons tomato paste
Cooked spaghetti, for serving

Add olive oil to a large pot over low heat and cook onions until caramelized, about 30 minutes.

While onions are cooking, pour canned tomatoes into a mixing bowl and mash into bite-size pieces using your hands or the back of a spoon.

Stir garlic and bell pepper into the pot with onions and cook on low heat for 3 to 4 minutes.

Deglaze onions, garlic, and pepper with wine and cook on medium heat until liquid is reduced by half, about 5 to 7 minutes.

Add sausage, ground sirloin, tomatoes, oregano, basil, and bay leaves. Continue cooking over low heat for 30 minutes.

Stir in cheese, parsley, balsamic vinegar, sugar, salt, chili flakes, and tomato paste. Simmer for at least 30 minutes and up to 1 hour, stirring occasionally. Remove bay leaves and discard.

Ladle sauce over cooked spaghetti. Top with additional Parmesan cheese if desired.