Heat a large pot or Dutch oven over medium-high heat. Add the ground beef, diced onion, and diced green bell pepper and sauté until the beef is browned and the vegetables are softened, about 6–8 minutes. Drain excess fat if desired.
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, and black pepper. If using Accent seasoning, add it now.
Bring the sauce to a gentle simmer, then reduce heat and simmer uncovered for about 20 minutes, stirring occasionally.
Stir the grated Parmesan into the sauce. Taste and add a pinch of salt and/or sugar if needed to balance acidity.
While the sauce simmers or after it finishes, bring a large pot with about 4 quarts of water to a boil. Add the spaghetti and stir until the water returns to a boil.
Reduce heat to a simmer and cook the spaghetti 8–9 minutes or until desired tenderness. Drain the pasta in a colander.
Serve the hot meat sauce over the drained spaghetti.