Combine flour and salt in a food processor. Add cold butter and pulse until mixture resembles coarse crumbs. Dissolve yeast in warm water, then add to the flour mixture. Process until dough forms, about 1 minute. Transfer to a bowl, cover, and refrigerate for 12-24 hours.
In a saucepan, melt butter over medium heat. Add grated onion and minced garlic, sauté for 4-5 minutes until softened. Add crushed tomatoes, peeled tomatoes (squashed), tomato paste, salt, sugar, oregano, basil, and red pepper flakes. Simmer over medium heat, stirring occasionally, until thickened (about 15-20 minutes).
In a bowl, mix ground pork with salt, sugar, paprika, sage, black pepper, chili flakes, garlic, fennel seed, and red wine vinegar until combined. Use as pizza topping.
Roll out dough to fit a greased 12-inch deep dish pan. Layer with mozzarella slices, provolone slices, Italian sausage, sauce, and additional toppings as desired (e.g., pepperoni). Bake at 425°F (220°C) for 35-40 minutes until crust is golden brown.
Let pizza cool for 10-15 minutes before slicing and serving.