Preheat the oven to 350°F (175°C).
Bring a large pot of salted water to a boil. Add the ziti pasta and cook according to package instructions until al dente, about 8-10 minutes. Drain and set aside.
In a large skillet, heat olive oil over medium heat. Add the chopped onion and cook until softened, about 4 minutes.
Add the minced garlic to the skillet and cook for 1 minute until fragrant.
In a large mixing bowl, combine the cooked onion and garlic, drained tuna, cream of mushroom soup, sour cream, milk, dried oregano, dried basil, salt, and black pepper. Stir until well combined.
Add the cooked ziti pasta to the mixture and gently fold to combine.
Stir in half of the mozzarella cheese and half of the cheddar cheese.
Transfer the pasta mixture to a greased 9×13 inch baking dish. Sprinkle the remaining mozzarella, cheddar, and Parmesan cheese evenly on top.
Bake in the preheated oven for 25-30 minutes, or until the casserole is bubbly and the cheese on top is melted and golden brown.
Remove from the oven and let the casserole rest for 5 minutes before serving.