Preheat your oven to 350°F (177°C) and prepare a 9x13-inch baking dish with nonstick spray.

In a large skillet, brown 1 pound of ground beef and 1 diced yellow onion over medium-high heat for 5–7 minutes.

Slice 2–3 russet potatoes into thin rounds and layer them in the prepared baking dish, seasoning with salt and pepper as you go.

Evenly distribute the cooked ground beef mixture over the potatoes, then layer with grated cheddar cheese.

In a bowl, mix one can of condensed cheddar soup, one can of evaporated milk, and 1 teaspoon of garlic powder until smooth.

Pour the creamy sauce over the layered ingredients and cover with aluminum foil. Bake for 60 minutes.

Remove the foil and bake for an additional 15 minutes until the top is golden brown.

Let the casserole cool for about 10 minutes before slicing and serving.