Preheat your oven to 375°F (190°C) and lightly grease a 9×13-inch baking dish.
Peel and thinly slice the potatoes into 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 the beef with garlic powder, onion powder, salt, and black pepper; stir well.
Layer half of the sliced potatoes evenly in the baking dish.
Top with half of the cooked beef mixture.
Repeat layers with remaining potatoes and beef.
Mix cream of mushroom soup with milk until smooth and pour evenly over casserole.
Sprinkle shredded cheddar cheese over the top and drizzle melted butter over the cheese.
Cover with foil and bake for 45 minutes.
Remove foil and bake an additional 15 minutes until cheese is bubbly and golden.
Let the casserole rest for 5-10 minutes before serving.
Sprinkle with paprika if desired and serve warm.