In a mixing bowl, combine the tomato sauce or pureed tomatoes, dried oregano, Italian seasoning, salt, ground black pepper, garlic (minced, paste, or granulated), granulated sugar, and onion powder if using. Mix thoroughly until cohesive. The sauce can be made ahead of time and even frozen for convenience. I always like to make extra sauce and freeze it for quick pizzas later!
Line a baking tray with aluminum foil and preheat your oven to 400° Fahrenheit (200° Celsius). This ensures even baking and makes cleanup easier.
Place the pita breads on the lined baking tray. Spread about 2 tablespoons of the prepared pizza sauce (from Step 1) onto each pita. Sprinkle each with about 1/2 cup of shredded mozzarella cheese (or your preferred cheese).
Evenly distribute the sliced red onions, bell pepper slices, mushrooms, cherry tomato halves, olives, thawed corn, and pickled jalapeño slices if using, over the cheese-topped pita breads. Sprinkle some salt, black pepper, dried oregano or pizza seasoning blend, and optional red chili flakes for flavor.
Transfer the assembled pita pizzas to the preheated oven and bake for about 15 minutes, or until the cheese is melted and starting to brown slightly. Let the pizzas rest on the tray for about 5 minutes after baking to set before slicing. For an air fryer, bake at 370° F for 5-7 minutes. I like to let my pizzas rest so the cheese doesn't slide off when slicing!
After resting, slice each pita pizza into four triangles. Serve immediately while hot and enjoy your homemade pita pizzas!