In a stand mixer, combine flour, cornmeal, salt, sugar, and yeast. Add warm water and melted butter, then knead with a dough hook on medium-low speed for 5 minutes.
Place the dough in a lightly greased bowl, cover with a damp cloth, and let rise in a warm environment for 60 to 90 minutes or until doubled in size.
Preheat oven to 425°F (218°C) and liberally grease a 12-inch deep-dish pizza pan with butter.
Roll the dough out on a floured surface to a 15-inch circle. Transfer to the pan, pressing the dough firmly against the bottom and 2 inches up the sides.
Layer the sliced mozzarella cheese across the bottom of the dough to create a moisture barrier.
Distribute the crumbled sausage, pepperoni, bacon, and ham evenly over the cheese layer.
In a medium bowl, stir together the crushed tomatoes, oregano, and garlic powder. Spread the sauce evenly over the meat layers.
Sprinkle the grated Parmesan cheese across the top of the tomato sauce.
Bake for 30 to 35 minutes until the crust is golden brown and the filling is bubbling.
Allow the pizza to rest in the pan for 15 minutes before slicing to allow the cheese and sauce to set.