• Preheat the oven to 350°F and lightly grease a 9x13-inch baking dish or two 8x8-inch baking dishes.
• Bring a large pot of salted water to a boil. Cook the rotini until just shy of al dente. Drain well and set aside.
• In a large skillet over medium heat, cook the ground beef until browned. If using diced onion, add it while the beef cooks and sauté until softened. Drain any excess grease.
• Stir in the Italian seasoning, garlic powder, onion powder, and black pepper.
• In a large mixing bowl, combine the cooked pasta, seasoned beef, pizza sauce, 1 cup of the mozzarella cheese, and most of the pepperoni. Stir until evenly combined.
• Spread the mixture into the prepared baking dish.
• Top with the remaining 1 cup mozzarella cheese and the rest of the pepperoni.
• Bake uncovered for 25 to 30 minutes, or until the cheese is melted and bubbly and the casserole is heated through.
• Let the casserole rest for 5 to 10 minutes before serving.

Freezer instructions:

To freeze before baking

• Assemble the casserole as directed, but do not bake.
• Let it cool completely.
• Wrap tightly with plastic wrap and then a layer of foil.
• Label and freeze for up to 2 to 3 months.

To bake after thawing

• Thaw the casserole in the refrigerator overnight.
• Remove from the refrigerator while the oven preheats.
• Bake at 350°F for 30 to 40 minutes, or until hot and bubbly.

To bake from frozen

• Remove the plastic wrap and keep the casserole covered with foil.
• Bake at 350°F for 60 to 75 minutes.
• Uncover and bake for an additional 10 to 15 minutes, until fully heated through and bubbly in the center.