Begin by bringing a large pot of salted water to a boil for the ziti. While waiting, prep your vegetables: slice the 3 zucchini into 1/4-inch rounds, chop the large onion, and mince the 3 garlic cloves. Measure out the fresh basil and parsley, and have all your cheeses and seasonings ready. Once the water boils, add the ziti and cook according to package directions until al dente, then drain and set aside. I like to reserve about 1/4 cup of the pasta water—it's great for loosening the sauce if needed later.

Heat 1/3 cup olive oil in a large skillet over medium-high heat until shimmering. Working in batches if needed to avoid crowding, add the sliced zucchini and cook for 4-5 minutes per side until golden brown and tender. Season with salt and pepper as they cook. Transfer the cooked zucchini to a plate and set aside. Browning the zucchini first develops a nice caramelized flavor and helps it stay firm when baked, rather than becoming mushy.

In a separate saucepan, heat the remaining 1/3 cup olive oil over medium heat. Add the chopped onion and cook for 5-7 minutes, stirring occasionally, until softened and translucent. Add the minced garlic and cook for 1-2 minutes until fragrant. Pour in the 56 oz of crushed tomatoes along with the dried oregano, and bring to a gentle simmer. Cook for 15-20 minutes, stirring occasionally, to allow the flavors to meld. In the final minute, stir in the fresh basil and parsley, and season with salt and pepper to taste. I find that simmering the sauce uncovered helps concentrate the flavors and reduce excess liquid slightly.

While the sauce finishes, preheat your oven to 350°F. In a large bowl, combine the cooked ziti from Step 1 with the finished sauce from Step 3, gently folding to ensure the pasta is evenly coated. The pasta will absorb some of the sauce flavors as it sits, so don't worry if it looks saucier than you'd expect—this is perfect for a baked pasta dish.

Divide the pasta-sauce mixture and browned zucchini between two 9x13-inch baking dishes (or similar size). For each pan, create two layers: spread half the pasta mixture on the bottom, dot with half the butter (about 2.5 tbsp per pan), then scatter half the browned zucchini. Sprinkle with half the mozzarella and half the Parmesan. Repeat with the remaining pasta, butter, zucchini, and cheeses for the second layer in each pan. The butter and cheese will melt into the pasta during baking, creating a rich, creamy texture throughout.

Place both baking dishes in the preheated 350°F oven and bake for 30 minutes until the cheese is melted and bubbly, and the edges are slightly golden. If you prefer a more deeply browned top, you can turn on the broiler for the final 2-3 minutes, but watch carefully to avoid burning. Let the casseroles rest for 5 minutes out of the oven before serving—this allows the layers to set slightly and makes serving cleaner.