In a large skillet over medium heat, brown the ground beef until cooked through. Drain any excess fat.
Add the chopped onion and minced garlic to the skillet. Sauté until the onion becomes translucent.
Transfer the beef mixture to a slow cooker. Stir in crushed tomatoes, tomato sauce, tomato paste, red wine (if using), sugar, basil, oregano, parsley, red pepper flakes, salt, and pepper.
Cover and cook on low for 6–8 hours or high for 3–4 hours, allowing the flavors to meld.
About 20–30 minutes before serving, cook the spaghetti according to package directions until al dente. Drain.
Stir the cooked spaghetti into the slow cooker, coating the pasta with sauce. Let it sit for 10 minutes so the flavors combine.
Serve hot and enjoy!
Serving and Storage Tips
