Preheat the Oven:
Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish with butter or cooking spray.
Cook the Pasta:
In a large pot, bring salted water to a boil and cook the pasta according to the package instructions. Drain and set aside.
Prepare the Casserole Mixture:
In a large mixing bowl, combine the drained tuna, cream of mushroom soup, milk, 1 cup of shredded cheddar cheese, Parmesan cheese, garlic powder, onion powder, salt, and pepper. Stir until well combined.
Add the Pasta and Peas:
Add the cooked pasta to the mixing bowl and fold it into the tuna mixture. If using peas, stir them in at this point.
Assemble the Casserole:
Transfer the tuna pasta mixture to the prepared baking dish. Spread it out evenly, then top with the remaining 1/2 cup of shredded cheddar cheese. If you like a crunchy topping, sprinkle the breadcrumbs over the top as well.
Bake the Casserole:
Cover the baking dish with aluminum foil and bake for 25-30 minutes. Remove the foil and bake for an additional 10 minutes to brown the top and make the cheese bubbly.
Serve and Enjoy:
Once the casserole is golden and bubbly, remove it from the oven and let it cool for a few minutes before serving. Enjoy your creamy, cheesy tuna casserole!