In a large pot or Dutch oven, brown the ground beef or Italian sausage over medium heat. Drain excess fat if necessary.
Add the finely diced onion and minced garlic to the pot, sautéing until the onion is translucent.
Pour in the crushed tomatoes, diced tomatoes (with their juice), dried basil, dried oregano, red pepper flakes (if using), salt, and pepper. Stir to combine.
Break the spaghetti in half and add it to the pot along with the beef or vegetable broth. Make sure the spaghetti is submerged in the liquid.
Bring the mixture to a boil, then reduce the heat to simmer. Cover the pot and cook for about 12-15 minutes, or until the spaghetti is tender, stirring occasionally to prevent sticking.
Once the spaghetti is cooked, adjust the seasoning to taste.
Serve the one-pot spaghetti hot, garnished with grated Parmesan cheese and fresh basil or parsley.
Enjoy the convenience and flavors of this one-pot spaghetti, providing a delicious and fuss-free meal with minimal cleanup.
