Preheat your griddle to medium heat.
Crisp the pepperonis. Lay the pepperonis on the griddle and cook for about 2-3 minutes until slightly crispy.
Cook the toppings. While the pepperoni cooks, add your diced onions, bell peppers, and any other raw toppings to the griddle. Season with salt and pepper. Cook until softened and lightly charred, then remove and set aside. (Everything that goes on top of this pizza needs to be fully cooked first - nothing cooks on its own once it's assembled.)
Mix the meat. In a bowl, combine the ground beef and ground Italian sausage. Mix well until fully combined.
Press the meat onto the tortilla. Lay one tortilla flat and press the meat mixture into a thin, even layer across the entire surface, just like you would with a smash taco.
Griddle the meat side down. Place the tortilla meat-side down on the griddle. Cook for 4-6 minutes, until the meat is browned and cooked through (internal temperature of 160°F for ground sausage).
Flip it. Using a large spatula or pizza peel, carefully flip the tortilla over so the meat is now facing up and the tortilla is on the griddle side. *You will need to use your spatula to scrape the meat from the griddle, because it will be sticking like a smash burger.
Build the pizza. Spread the pizza sauce over the meat, then top with 1 cup of the shredded mozzarella. Add the crispy pepperonis and your cooked veggies. Let it cook until the cheese is about halfway melted.
Remove and set aside. Once the cheese is halfway melted, use your spatula or pizza peel to lift the whole pizza off the griddle and set it aside.
Prep the stuffed crust tortilla. Spread the butter on one side of the second tortilla, then top that same side with the grated parmesan cheese (and Italian herbs or red pepper flakes, if using).
Griddle the crust tortilla. Place the second tortilla buttered-side down on the griddle. Immediately top it with the remaining 1 cup of mozzarella cheese.
Stack the pizza on top. Using your spatula, carefully lift the first tortilla pizza and place it directly on top of the melting cheese layer on the second tortilla, still on the griddle.
Melt and combine. Dome the pizza with a cover, or close the griddle lid briefly, until all the cheese is fully melted and the bottom tortilla crust is golden brown. *If needed, turn the griddle heat down to low or turn the burners off so the tortilla doesn't burn on the bottom.
Rest and slice. Remove from the griddle and let it rest on a cooling rack for a few minutes so the bottom stays crisp. Slice like a pizza and serve.