Bring a large pot of salted water to a rolling boil. Add the thick spaghetti and cook until al dente, according to package instructions. Drain and set aside without rinsing.

In a large, heavy-bottomed pot or Dutch oven, heat the olive oil over medium-high heat. Add the Italian sausage and ground beef. Cook, breaking up the meat with a wooden spoon, until well-browned and fully cooked through. Drain excess fat if necessary.

To the same pot, add the diced onion, garlic, and green bell pepper. Sauté for 3–4 minutes, stirring frequently, until the vegetables are softened and aromatic.

Stir in the tomato paste, granulated sugar, garlic powder, dried oregano, dried basil, onion powder, and cayenne pepper. Mix well until the spices are evenly distributed and the tomato paste is fully integrated.

Pour in the crushed tomatoes and water, scraping the bottom of the pot to release any browned bits. Stir thoroughly. Bring the sauce to a gentle simmer and allow it to cook uncovered for approximately 30 minutes, stirring occasionally.

After the sauce has thickened and the flavors have developed, season to taste with kosher salt and black pepper. Add the cooked spaghetti and parmesan cheese directly to the sauce. Toss gently until the pasta is evenly coated and the cheese is melted throughout.

Serve immediately, garnished with additional parmesan or chopped parsley if desired.