Adjust oven rack to 6 to 8 inches below broiler element and preheat broiler to high. Heat oil in a large cast iron skillet over high heat. Turn off heat and wipe out excess oil with paper towel.
Place tortilla in skillet with the rougher textured - side facing down. Spread sauce evenly over tortilla all the way to the edges. Spread mozzarella and half of parmesan evenly over tortilla all the way to the edges. Sprinkle with onion and bell pepper. Lay pepperoni and sausage chunks over pizza.
Place skillet under broiler and broil until cheese is melted and starting to brown in spots, 2-4 minutes. Remove from oven and sprinkle with remaining parmesan cheese.
Set pan on stove top and turn heat on medium to cook the bottom to brown and crispy. Using a small spatula, gently pry edges of pizza, releasing the cheese from the skillet. Slide pizza out onto cutting board. Cut and serve immediately.