Preheat the Oven:

o Preheat your oven to 375°F (190°C).

o Coat a 9x13-inch baking dish with butter or a non-stick spray to prevent sticking.

Cook the Pasta:

o Fill a large pot with water, add salt, and bring it to a rolling boil.

o Once boiling, add the penne pasta and cook as directed on the package until it reaches an al dente texture.

o Drain the pasta and set it aside for later use.

Cook the Sausage and Vegetables:

o In a large skillet, cook the Italian sausage over medium heat until browned and cooked through, breaking it up into crumbles as it cooks.

o In the same skillet, add the chopped onion and bell pepper. Sauté for 4-5 minutes until softened.

Combine Ingredients:

o Return the cooked sausage to the skillet with the sautéed vegetables.

o Add the sliced pepperoni, drained black olives, and marinara sauce.

o Stir well to combine, and let the mixture simmer for 5 minutes to meld the flavors.

Assemble the Baked Ziti:

o In a large mixing bowl, combine the cooked pasta with the sausage and sauce mixture. Toss until the pasta is evenly coated.

o Transfer half of the pasta mixture into the prepared baking dish.

o Add the remaining pasta mixture on top and finish with the remaining 1 1/4 cups of mozzarella cheese.

Bake:

o Tent the baking dish with aluminum foil and place it in the preheated oven for 20 minutes.

o After that, take off the foil and continue baking for another 10 minutes, or until the cheese is fully melted and bubbly.

Serve:

o Remove the baked ziti from the oven and let it rest for a few minutes before serving.