01 -
Heat a large saucepan or Dutch oven over medium heat. Add ground beef and Italian sausage to the pan. Season with Italian seasoning and salt, breaking up the meat with a spoon. Cook until browned, about 7-9 minutes.
02 -
Add crushed tomatoes, red wine vinegar, butter, and sugar to the meat mixture. Stir to combine. Submerge the onion half (leave whole) into the sauce. Simmer over low heat for 20-30 minutes. Remove the onion before serving.
03 -
While the sauce is simmering, cook the spaghetti according to package instructions until al dente. Drain and set aside.
04 -
Serve the meat sauce over the cooked spaghetti. Top with grated Parmesan cheese and red pepper flakes to taste.