Preheat the oven to 475°F (245°C). Lightly spray a pizza pan or baking sheet with non-stick cooking spray.
Spread the 1 lb pizza dough into a 16–18 inch round on the prepared pan, shaping an edge for the crust.
Brush the dough edges with half of the melted butter and sprinkle all of the garlic salt over the edges and crust; concentrate the seasoning on the perimeter.
Bake the crust for 8 minutes until it begins to set but is not fully browned.
While the crust bakes, cook 1/2 lb spaghetti or spaghettini to al dente according to package instructions, then drain.
In a mixing bowl, toss the cooked spaghetti with 2 cups of the prepared marinara (reserve 1/2 cup for topping).
When the crust comes out of the oven, brush the edges with the remaining melted butter. Spread the sauced spaghetti evenly over the crust.
Spoon the reserved 1/2 cup marinara over the top of the pasta to keep it moist, then sprinkle 1½ cups grated mozzarella evenly over the pizza.
Return the pizza to the oven and bake 2–3 minutes more, or until the cheese is completely melted.
Remove from the oven and let cool 5–10 minutes. Garnish with parsley if desired, slice, and serve with extra marinara for dipping.