Heat a large pot or Dutch oven over medium-high heat. Add the ground beef, diced onion, and diced green bell pepper and cook, stirring occasionally, until the beef is browned and vegetables are softened, about 6–8 minutes.
Add the tomato sauce, stewed tomatoes (with their juices), water, and the bouillon cubes to the pot. Stir to combine.
Stir in the dried basil, dried oregano, chili powder, parsley flakes, garlic powder, black pepper, and Accent seasoning if using. Bring the mixture to a simmer.
Reduce heat to maintain a gentle simmer and cook, uncovered, for 20 minutes, stirring occasionally so the bouillon dissolves and flavors meld.
Stir in the grated Parmesan. Taste the sauce and add a pinch of salt and/or a pinch of sugar if needed to balance acidity.
Meanwhile, bring a large pot with 4 quarts of water to a boil. Add the spaghetti and stir until the water returns to a boil, then reduce heat to maintain a gentle boil and cook 8–9 minutes until al dente.
Drain the spaghetti in a colander. Serve the cooked spaghetti with the meat sauce spooned over or alongside.