Prepare the dough by bringing it to room temperature for about 30 minutes. Preheat your oven to 400°F (200°C) and position the rack in the top section.

In the skillet, heat 1 tablespoon of olive oil over medium heat. Add the Italian sausage, breaking it apart as it cooks, and stir in a pinch of red pepper flakes. Cook for about 5-7 minutes until browned, then strain the sausage and transfer it to a bowl.

Add another tablespoon of olive oil to the same skillet and heat. Add sliced mushrooms and sauté until golden brown, about 4-5 minutes, then transfer to the sausage bowl.

In the skillet, add green bell peppers and onion slices. Cook for about 2 minutes, stirring frequently until soft but still slightly crisp. Layer the sautéed vegetables at the bottom of the skillet.

Layer cooked bell peppers and onions first, then fill in gaps with pepperoni, sautéed mushrooms, and browned sausage all on top.

Sprinkle two tablespoons of grated Parmesan cheese evenly over the toppings, followed by shredded mozzarella and provolone slices.

Spread the pizza sauce evenly over the cheese layer.

Roll out the pizza dough to about 12 inches in diameter and place it over the filling, tucking the edges around the skillet.

Brush the top of the dough with the remaining olive oil. Bake for 20-25 minutes until crust is golden brown and edges are puffed.

Once baked, allow to cool for a minute, then carefully flip the skillet onto a pizza pan to serve it right-side up.

After the second bake, sprinkle with remaining Parmesan cheese and allow to cool slightly before slicing.