Preheat your oven to 375°F (190°C). While it heats up, cook and drain the Italian sausage. Place it in a bowl and set aside.

In a large saucepan, bring 6 cups of salted water to a boil. Cook the lasagna noodles for about 7 minutes until they are al dente. Remove from water, cut them to size if needed, and set aside.

Prepare the tomato sauce by heating olive oil in a large skillet over medium-high heat. Add the chopped onions and cook until they are translucent. Stir in the minced garlic and optional red crushed pepper until fragrant. Add the crushed tomatoes and remaining sauce ingredients. Cover and let it simmer for 20-25 minutes.

In a 9x13x3-inch baking dish, spread 1 cup of the prepared tomato sauce on the bottom. Layer with lasagna noodles, followed by ricotta, mozzarella, cooked sausage, pepperoni, and a sprinkle of parmesan. Repeat the layering process, finishing with mozzarella, more pepperoni, parmesan, and a dash of Italian seasoning on top.

Bake in the preheated oven for 45 minutes. Once done, let it cool for about 10 minutes before cutting into sections and serving.