Bring a large pot of salted water to a boil and cook noodles for one minute less than the package directions state.
While noodles are cooking, preheat oven to 375 degrees. Spray a 9x13 baking dish with nonstick spray.
Add the tuna, cream of mushroom, cream of celery, peas, milk, fried onions, garlic powder, and pepper to a mixing bowl and stir to combine.
When pasta is done cooking, drain, and add noodles to the tuna mixture. Stir well.
Pour the noodles into the prepared baking dish and bake, covered with foil, for 25 minutes.
While the casserole is baking, stir together the topping ingredients.
Remove the foil from the casserole and sprinkle the cracker crumbs over the top. Return to the oven for 10 minutes.
Sprinkle with fresh parsley or dill before serving.