Preheat your oven to 350°F (175°C).

In a large skillet over medium heat, brown the ground beef and chopped onion for 5-7 minutes, then drain excess fat.

Stir in cream of mushroom soup, ketchup, and water, followed by garlic powder, Worcestershire sauce, salt, and pepper. Simmer for 2-3 minutes.

Grease a 9x13-inch baking dish and layer half of the sliced potatoes, half of the beef mixture, and half of the cheddar cheese.

Repeat layering with remaining ingredients, gently pressing down.

Cover with aluminum foil and bake for 1 hour.

Uncover and bake for an additional 20 minutes until cheese is bubbly and golden.

Let it rest for a few minutes before serving, garnishing with green onions if desired.