Step 1: Preheat and Prepare
Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish and set aside.

Step 2: Cook the Beef Mixture
In a large skillet over medium heat, cook the ground beef until browned, breaking it apart with a spoon. Once browned, drain any excess grease. Add the diced onion and garlic and sauté for 2–3 minutes, or until the onion becomes translucent and fragrant.

Step 3: Add Sauce and Seasoning
Stir in the pizza sauce and Italian seasoning. Season with salt and pepper to taste. Let the mixture simmer for about 3–5 minutes, allowing the flavors to combine and the sauce to slightly thicken.

Step 4: Layer the Casserole
Transfer the beef mixture to the prepared baking dish and spread it out evenly. Sprinkle half of the mozzarella cheese over the top of the beef mixture. Next, add the sliced pepperoni and any additional desired toppings (such as sliced mushrooms, chopped bell peppers, or olives) in an even layer over the cheese.

Step 5: Add the Tater Tots
Arrange the frozen tater tots in a single, even layer over the entire top of the casserole. Don’t worry if they’re tightly packed—this is where the crispy magic happens!

Step 6: Bake and Finish
Place the casserole in the preheated oven and bake for 25–30 minutes, or until the tater tots are golden brown and crispy. Remove the casserole from the oven, sprinkle the remaining mozzarella cheese on top, and return it to the oven for an additional 5–7 minutes, until the cheese is fully melted and bubbly.

Step 7: Rest and Serve
Allow the casserole to cool for 5–10 minutes before slicing and serving. This helps the layers settle and makes it easier to plate.