Preheat the oven to 375°F and lightly grease a 9x9 baking dish.
Cook the egg noodles in a large pot of boiling water until just tender, then drain and return them to the pot.
Stir the cream of mushroom soup, milk, garlic powder, salt, and pepper into the noodles until evenly combined.
Add the drained tuna, frozen peas, and 1 1/2 cups of the cheddar cheese. Mix gently until the ingredients are distributed.
Transfer the mixture to the prepared baking dish and spread it into an even layer.
Sprinkle the remaining 1/2 cup of cheddar cheese over the top.
Bake for 20 to 25 minutes until the cheese is melted and the edges are bubbling. Let it rest for 5 minutes before serving.