In a small bowl, dissolve sugar and yeast in warm water. Allow it to stand for 5-10 minutes until it becomes frothy.

In a large bowl, mix the flour, cornmeal, and salt. Create a well in the center and pour in the yeast mixture, melted butter, and olive oil. Stir until a dough forms.

Knead the dough on a floured surface for 5-7 minutes until it’s smooth and elastic. Place it in a greased bowl, cover, and let it rise for 1-1.5 hours, or until it doubles in size.

In a medium saucepan, heat olive oil. Add chopped onion and sauté for about 4-5 minutes, until softened. Stir in the minced garlic and cook until fragrant, about 1-2 minutes.

Add the crushed tomatoes, tomato paste, oregano, basil, red pepper flakes (if using), and sugar. Season with salt and pepper, then simmer for 20-25 minutes, stirring occasionally, until the sauce thickens.

In a skillet, cook the Italian sausage until browned and crumbled. Drain excess fat, and if using, sauté the bell pepper and onion until softened.

Preheat your oven to 425 degrees F (220 degrees C) and grease a 9-inch or 10-inch deep-dish pizza pan.

Punch down the dough and roll it into a 12-inch circle. Place it in the pan, pressing it to create a thick crust.

Layer half of the mozzarella, then the provolone, followed by the Parmesan cheese. Add the sausage, bell pepper, and onion (if using), then pour the tomato sauce over the filling.

Bake for 30-40 minutes until the crust is golden brown and the cheese is bubbly. If the edges brown too quickly, cover them with foil.

Let the pizza cool for 5-10 minutes before slicing and serving.