Preheat oven to 400°F. Spray 13x9-inch glass baking dish with cooking spray. Place uncooked noodles in baking dish; top evenly with undrained tuna. Set aside.
Place water, cream cheese, Parmesan cheese, salt and pepper in medium microwave-safe bowl. Microwave on HIGH 4 minutes or until boiling, stirring once halfway. Carefully pour hot mixture over tuna and noodles.
Cover dish tightly with aluminum foil; bake 15 minutes. Add peas; stir. Sprinkle with Cheddar cheese and cover again with foil. Bake 15 minutes more or until noodles are tender. Top with crushed pretzels just before serving.