Preheat oven to 475 degrees. Spray pizza pan with non-stick cooking spray.
Spread pizza dough out to be 16-18'' across. Place on prepared pizza pan. Brush crust with half melted butter and all the garlic salt, concentrating on the edges. Bake crust for 8 minutes.
Mix cooked spaghetti with 2 cups of prepared sauce.
Once crust comes out of the oven, brush edges with remaining melted butter. Top with coated spaghetti and spoon on remaining 1/2 cup of sauce to keep pasta moist. Top with grated cheese and bake 2-3 minutes more until cheese has completely melted. Remove from oven and cool 5-10 minutes. Top with parsley if desired. Cut into pieces and enjoy!