Cut hot dogs in half lengthwise; cut into 1/2-in slices. In a large skillet, brown hot dogs over medium-high heat. Reduce heat. Add onion and butter; cook until onion is tender. Stir in the macaroni, soup, water and mustard.
Pour into a greased 11 x 7 x 2 inch baking dish. Sprinkle with bread crumbs. Bake, uncovered at 350 for 25-30 minutes or until bubbly.
Yield: 4 servings