Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish.
Peel and slice the potatoes into thin, even rounds.
In a large skillet over medium heat, cook ground beef and chopped onion until beef is browned and onions are soft, about 5-7 minutes. Drain excess grease.
Season beef with garlic powder, onion powder, salt, and black pepper. Stir well.
Spread half of the sliced potatoes evenly in the baking dish.
Add half of the cooked ground beef mixture over the potatoes.
Repeat layers with remaining potatoes and beef.
In a small bowl, mix cream of mushroom soup and milk until smooth. Pour over casserole layers.
Sprinkle shredded cheddar cheese on top and drizzle with melted butter.
Cover casserole with foil and bake for 45 minutes.
Remove foil and bake an additional 15 minutes until cheese is bubbly and golden.
Let casserole rest for 5-10 minutes before serving.
Sprinkle with paprika if desired and serve warm.