In large skillet, brown ground beef and onion. Stir in tomatoes, tomato paste, salt, parsley, garlic salt and pepper, and simmer over low heat for 3 hours.
Preheat oven to 350 degrees F (175 degrees C). Bring a large pot of lightly salted water to a boil.
Add pasta and cook for 8 to 10 minutes or until al dente; drain.
In a 2 quart casserole dish, combine noodles and meat mixture. Top with cheese slices and bake for 15 to 20 minutes, or until cheese is melted.