Preheat the oven to 375°F. Grease a 9x13 inch baking dish and set aside.
Cook the pasta according to package instructions until al dente. (3 to 5 minutes) Drain and set aside.
In a large saucepan over medium-high heat, combine the diced tomatoes, marinara sauce, garlic salt, oregano, onion powder, basil, and black pepper. Bring the mixture to a simmer and cook for 5 minutes.
Combine the cooked pasta with the sauce mixture. Stir in the grated Parmesan cheese.
Transfer the pasta mixture to the prepared baking dish. Sprinkle the mozzarella cheese over the top, followed by the mini pepperoni.
Bake in the preheated oven for 20 minutes, or until the cheese is melted and bubbly.
Notes
STORAGE & FREEZING
LEFTOVERS: To store leftovers, allow them to cool to room temperature. Then, transfer to an airtight container and refrigerate for 3 to 5 days.
FREEZING: For longer storage, this casserole freezes really well. Wrap it tightly in plastic wrap and aluminum foil, or place it in a freezer-safe container, where it can last for up to 3 months.
REHEATING: When ready to eat, reheat or bake the casserole in a 350 degree oven until bubbly. If it is pre-baked, you can use the microwave in 30 second intervals. If the casserole is frozen, thaw it in the refrigerator overnight for best results.