Preheat your oven to 375°F (190°C).

In a large skillet over medium heat, add the ground beef and cook for about 7-10 minutes until browned. Drain excess fat.

In the same skillet, sauté the chopped onion for 3-4 minutes until translucent. Season with salt, pepper, and garlic powder.

Peel and thinly slice the potatoes. Grease a baking dish and layer half of the potato slices at the bottom, seasoning lightly with salt and pepper.

Spread the beef and onion mixture over the potato layer, then add the remaining potato slices on top.

Whisk together the milk and melted butter in a small bowl. Pour this mixture over the layers in the baking dish.

Generously sprinkle the shredded cheese over the top of the casserole.

Cover the baking dish with aluminum foil and bake for 45 minutes. Afterward, remove the foil and bake for another 15-20 minutes until cheese is bubbling and golden.

Let it rest for 10 minutes before serving.