Heat a large saucepan over medium-high heat. Add the ground beef and break it up with a meat masher or wooden spoon. Cook until browned, then drain and discard excess grease.
Add the salt, black pepper, chopped yellow onion, minced garlic, Italian seasoning, dried parsley, garlic powder, red pepper flakes (if using), Worcestershire sauce, sugar, and dried basil to the browned beef. Stir and cook until the onion is soft and translucent.
While the onions cook, heat 1 cup of water in a microwave-safe bowl for 2–3 minutes. Crumble in the Knorr Tomato Bouillon Cube and stir until fully dissolved.
Stir in the two cans (15 oz each) of tomato sauce, the tomato paste, and the hot water with dissolved bouillon. Bring the mixture to a boil, then reduce heat, cover, and simmer for 30 minutes, stirring occasionally.
While the sauce simmers, cook the spaghetti noodles according to the package directions in a pot of boiling, salted water. Drain the pasta when done.
Serve the sauce over the cooked spaghetti.