1. Heat oven to 450 degrees F. Coat a rimmed baking sheet and a 10-inch deep-dish pizza pan with nonstick cooking spray.
2. Place eggplant, mushrooms and onion on prepared baking sheet. Bake at 450 degrees F for 30 minutes, turning once.
3. On a lightly floured surface, roll out dough to form a circle slightly larger than the pizza pan. Place dough in prepared pan, pressing excess dough to the sides.
4. Layer half the cheese and all the vegetables onto dough. Season with salt, oregano and pepper. Spoon sauce over vegetables and scatter pepperoni over sauce.
5. Bake at 450 degrees F for 15 minutes. Scatter remaining cheese and fan tomato slices over top. Bake for an additional 15 minutes. Remove from oven and cool slightly.
6. Use a sharp knife to cut into 6 slices; remove with pie server or spatula.