Sauté the aromatics. Heat 1–2 tablespoons olive oil in a skillet over medium heat. Add diced onion and a pinch of salt. Cook 5–7 minutes until soft and lightly golden. Stir in garlic and cook 30–60 seconds until fragrant.

Brown the meat (if using). Add ground beef or sausage to the skillet. Break it up and cook until browned, 6–8 minutes. Drain excess fat if needed. Season with salt and pepper.

Load the slow cooker. Add crushed tomatoes, tomato sauce, tomato paste, sautéed onion and garlic, and meat (if using) to the slow cooker.

Season it right. Add bay leaves, oregano, basil, red pepper flakes, ground fennel, 1 teaspoon sugar (or grated carrot), 1 teaspoon balsamic, 1 teaspoon salt, and several grinds of black pepper. If you have a Parmesan rind, toss it in.

Set and forget. Cover and cook on Low for 6–8 hours or High for 3–4 hours, stirring once or twice if convenient.

Finish and adjust. Remove bay leaves and Parmesan rind. Taste and adjust salt, pepper, sugar, and balsamic. If it’s too thick, stir in a splash of water or broth. If it’s thin, cook uncovered on High for 20–30 minutes.

Brighten it up. Stir in chopped fresh basil or parsley right before serving for a fresh finish.

Serve. Toss with hot spaghetti and a little pasta cooking water to help it cling. Finish with grated Parmesan and a drizzle of good olive oil.