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 beef mixture with garlic powder, onion powder, salt, and black pepper. Stir well.
Layer half the sliced potatoes evenly on the bottom of the prepared baking dish.
Spoon half of the cooked ground beef mixture over the potatoes.
Repeat with remaining potatoes and beef mixture.
In a small bowl, mix the cream of mushroom soup with milk until smooth.
Pour the soup mixture evenly over the casserole, ensuring it seeps into all layers.
Sprinkle shredded cheddar cheese over the top and drizzle melted butter over the cheese.
Cover the dish with aluminum foil and bake for 45 minutes.
Remove foil and bake for 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 scoop into portions to enjoy.