1. Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish with a bit of butter.
2. In a large skillet, melt the butter over medium heat. Add the chopped onion and bell pepper, sautéing until the onion is translucent and the pepper is tender.
3. Add the sliced hot dogs to the skillet and cook until they start to brown slightly, about 5 minutes.
4. In a large mixing bowl, combine the cream of mushroom soup, milk, mustard, garlic powder, salt, and pepper. Stir until smooth.
5. Add the cooked macaroni, hot dog mixture, and half of the cheese to the bowl. Mix everything until well combined.
6. Pour the mixture into the prepared baking dish, spreading it evenly. Sprinkle the remaining cheese over the top. If desired, add breadcrumbs for a crispy topping.
7. Bake in the preheated oven for 25-30 minutes, or until the cheese is bubbly and golden on top.
8. Let it cool for a few minutes before serving, allowing the flavors to meld together beautifully.

Remember, patience is key. Mama Lou would always say, “The waiting makes it taste even better!”