Preheat your oven to 375°F (190°C) and grease a 9x13-inch baking dish with olive oil.

In a large skillet, cook ground beef and chopped onion over medium heat until the beef is browned and onions are translucent, about 5-7 minutes. Drain excess fat and set aside.

Mix garlic powder, salt, and black pepper into the beef and onion mixture until well-combined.

In a mixing bowl, whisk together condensed cream of mushroom soup and milk until smooth.

Layer half of the sliced potatoes in the baking dish, followed by half of the beef mixture and half of the cream mixture. Repeat layers.

Cover the baking dish with aluminum foil and bake for 45 minutes.

Remove the foil, sprinkle shredded cheddar cheese over the top, and bake for an additional 15 minutes until cheese is bubbly and golden.