Start by cooking your pasta in a large pot of well-salted water. Drain the pasta a couple minutes before it's fully done - it'll finish cooking in the oven.
1 pound short pasta (campanelle, ziti, penne, rigatoni, etc)
While the pasta is cooking, preheat your oven to 375°F.
Heat a large pan over medium heat and add the pepperoni slices. Cook for a few minutes until they crisp up and release some of their fat, then remove them to a paper towel-lined plate to drain. (If you'd rather do this in the oven, spread the pepperoni on a baking sheet and bake at 375°F for about 8-10 minutes until crispy.)
8 ounces pepperoni slices
In the same pan, sauté the onion over medium heat for a few minutes until it turns translucent.
1 small onion, finely chopped
Add the garlic and cook for another 30 seconds, then remove the onion and garlic from the pan and set aside.
2 cloves garlic, minced
Brown the ground beef and/or sausage in the same pan, breaking it up as it cooks.
1 pound ground beef and/or ground Italian sausage
Once the meat is browned, add the tomatoes, Italian seasoning, salt, pepper, red pepper flakes if using, and the sautéed onion and garlic. Break up the plum tomatoes with tongs as everything simmers together. Let it simmer for about 10 minutes.
28 ounces canned plum tomatoes, 2 teaspoons Italian seasoning, ½ teaspoon salt, ½ teaspoon pepper, ½ teaspoon red pepper flakes (optional)
Drain the pasta and toss with the sauce right in the pot.
Now for the fun part! In a casserole dish, layer half the pasta, then half the mozzarella, then half the Parmesan, then half the basil, parsley, and pepperoni. Repeat with the remaining half of everything so you end up with two layers.
1 pound short pasta (campanelle, ziti, penne, rigatoni, etc), 1 pound fresh mozzarella, ¼ cup Parmesan cheese, 2 Tablespoons chopped fresh basil, 2 Tablespoons chopped fresh parsley, 8 ounces pepperoni slices
Bake for 20 minutes, until the cheese is melted and bubbly.
Let it sit for a few minutes before serving - it'll be easier to scoop and a lot less likely to burn the roof of your mouth. Enjoy!