Authentic Chicago deep dish pizza with a buttery, layered crust, slightly sweet tomato sauce, and a thick layer of mozzarella and parmesan. Makes two 9-inch deep dish pizzas.
Read through the entire recipe before beginning. You will need two deep dish 9x2-inch round cake pans (or 9-inch springform pans) if making both pizzas at the same time.
Combine the flour, cornmeal, salt, sugar, and yeast in the bowl of a stand mixer fitted with a dough hook. Add the warm water (around 90°F/32°C) and 1/4 cup melted butter. Mix on low speed until moistened, then continue beating until the dough is soft and supple and pulls away from the sides of the bowl, about 4-5 minutes.
If dough is too tough, beat in 1 teaspoon warm water. If too soft, beat in 1 tablespoon flour.
Remove the dough from the bowl and form into a ball. Lightly grease a large bowl with olive oil, place the dough inside and turn to coat all sides. Cover tightly with aluminum foil and let rise in a warm environment for 1-2 hours until doubled in size.
On a lightly floured surface, punch down the dough and roll into a 15x12-inch rectangle. Spread 1/4 cup softened butter on top. Roll up lengthwise, then cut the log in half. Form two dough balls, place back in the greased bowl, cover with foil, and refrigerate for 1 hour until puffy.
Melt butter in a medium saucepan over medium heat. Add grated onion, salt, oregano, and red pepper flakes. Cook until onion is slightly browned, about 5 minutes. Add garlic, crushed tomatoes, and sugar. Reduce heat to low-medium and simmer until thick and fragrant, about 30 minutes. You should have about 2 1/2 cups of sauce.
Sauce can be refrigerated in a covered container for up to 2 days or frozen for up to 2 months.
Preheat oven to 425°F (218°C).
Working with one dough ball at a time (keeping the other refrigerated), roll out on a lightly floured surface into a 12-inch circle. Drape over a 9x2-inch deep dish cake pan and press firmly into the pan. Trim excess dough. Brush the top edges with olive oil. Fill each pizza with 2 cups mozzarella, then desired toppings (pepperoni, bacon), then pour about 1 1/4 cups sauce on top. Sprinkle with 1/4 cup parmesan. Repeat with second dough ball.
Place the cake pans on a large baking sheet. Bake for 20-28 minutes until the crust is golden brown. After 15 minutes, loosely cover with aluminum foil if browning too quickly. Remove from oven and cool in pans on a wire rack for 10 minutes before slicing and serving.
Store leftover pizza in an airtight container in the refrigerator for up to 5 days. Reheat in a 300°F oven for 15-20 minutes.