- Cooking spray
- 2 teaspoons butter
- 1 large Spanish onion, halved and sliced thinly
- 2 pounds Yukon Gold potatoes, sliced thinly
- 1 teaspoon salt
- 1/4 teaspoon black pepper
- 1/8 teaspoon ground nutmeg
- 2 cups whole milk
- 4 ounces low-fat extra-sharp shredded Cheddar cheese
Preheat the oven to 350 degrees.
Coat a 9-by-13-inch glass baking dish with cooking spray. Generously coat a large pot with cooking spray and heat over medium heat. When hot, melt the butter. Add the onion to the pot and cook, stirring occasionally, until the onion starts to turn translucent and caramelize, about 10 minutes.
Add the potatoes, salt, pepper, nutmeg, milk, and cheese to the pot. Toss several times to coat each slice of potato. Bring to a boil and cook, stirring occasionally, until the sauce thickens enough to coat the back of a spoon, about 5 minutes.
Pour potato mixture into the baking dish and bake until the top is golden and potatoes are tender, about 45-60 minutes. Slice into 8 pieces and serve.