1. Preheat the Oven
Set your oven to 350°F (177°C). Lightly coat a 9×13-inch baking dish with nonstick spray to prevent sticking. Set aside.

2. Cook the Ground Beef
In a large skillet over medium-high heat, cook the ground beef and diced onion. Season with salt and pepper, breaking up the meat as it browns. Once fully cooked and no longer pink, drain any excess fat and set aside.

3. Assemble the Casserole
Layer sliced potatoes evenly in the prepared baking dish, seasoning each layer with salt and pepper. Add 1/4 of the cooked beef and onion mixture, then sprinkle 1/4 of the shredded cheddar cheese over the top. Repeat this layering process three more times to ensure even distribution of ingredients.

4. Prepare the Sauce
In a small bowl, whisk together the condensed cheddar soup, evaporated milk, milk, and garlic powder until smooth and well combined.

5. Bake the Casserole
Pour the prepared sauce evenly over the assembled layers. Cover the dish tightly with aluminum foil and bake for 60 minutes. Then, remove the foil and bake for an additional 15 minutes until the top is golden brown and the sauce is bubbling.

6. Serve and Enjoy
Remove the casserole from the oven and let it rest for a few minutes before serving. This allows it to set properly and enhances the flavors. Serve warm and enjoy!