Tuna Noodle Casserole

Found this recipe from New Cookbook. Absolutely love it! Noodle with creamy sauce, tuna flake, and crunchy top, hmmm, so yummy!

8 ounces spaghetti, cooked, drained (or use dried wide noodles)
3/4 cup chopped sweet pepper (1 medium)
1 cup chopped celery (2 stalks)
1/4 cup chopped onion
1/4 cup butter
1/4 cup all-purpose flour
1/2 tsp salt
1/4 tsp black pepper
2&1/4 cups milk
2 cans (5-ounce each) chunk light tuna, drained
1/2 cup Japanese-style bread crumbs
1/4 cup grated parmesan cheese
1 tbsp snipped parsley
1 tbsp butter, melted

    Preheat oven to 375 degrees. Lightly grease a 2-quart baking dish. Cook noodles and drain.
    For sauce, in a skillet cook sweet pepper, celery, onion in 1/4 cup hot butter until tender. Stir in flour, salt, black pepper. Add milk. Cook and stir until thickened and bubbly. Fold in tuna and cooked noodles.    
    Transfer the mixture into the baking dish.
    In a bowl combine bread crumbs, cheese, parsley and melted butter. Sprinkle crumb mixture over noodle mixture. Bake, uncovered, for 25-30 minutes.