Preheat the oven to 375 degrees and lightly grease a 9x13 baking dish.
Bring a large pot of salted water to a boil and cook the egg noodles until just tender. Drain and set aside.
In a large mixing bowl, stir together the cream of mushroom soup, milk, garlic powder, salt, and pepper until smooth.
Add the drained tuna, frozen peas, cooked noodles, and 1 cup of the shredded cheddar cheese to the bowl. Mix gently until everything is evenly coated.
Transfer the mixture to the prepared baking dish and spread it into an even layer.
In a small bowl, combine the panko breadcrumbs, melted butter, and remaining 1/2 cup cheddar cheese. Sprinkle this mixture evenly over the top of the casserole.
Bake for 25 to 30 minutes until the topping is golden brown and the edges are bubbling. Let it rest for a few minutes before serving.