Preheat the oven to 400°F. Grease a 9x13 baking dish with cooking spray.
Slice the onions and potatoes into thin strips, about 1/4 inch in size.
½ yellow onion, 4 pounds Yukon gold potatoes
In a medium skillet, melt the butter over medium heat.
3 Tablespoons unsalted butter
Slowly whisk in the gluten-free flour. Then, add the milk and vegetable broth, whisking continuously.
2 ½ cups milk, ¼ cup 1:1 all-purpose gluten-free flour, 1 cup vegetable broth
Add the minced garlic, garlic powder, onion powder, thyme, salt, and pepper. Cook 2-3 minutes or until the sauce coats the back of a spoon, stirring frequently. Remove the skillet from the heat.
3 teaspoons minced garlic, 2 teaspoons kosher salt, ½ teaspoon black pepper, 1 teaspoon onion powder, 1 Tablespoon fresh thyme, 1 teaspoon garlic powder
Layer half the potatoes evenly in the bottom of the baking dish. It's okay if they overlap slightly!
Sprinkle the onions evenly on top.
Pour half the creamy sauce evenly over the onions and potatoes.
Sprinkle 1 cup of cheese on top.
2 cups shredded cheddar cheese
Repeat, adding a second layer of potatoes, onions, sauce, and cheese.
Cover the dish with aluminum foil. Bake for 30 minutes.
Remove the foil, and continue to bake 25-30 minutes or until the potatoes are fork-tender, the cheese is lightly browned, and the sauce is bubbling around the edges.
Cool slightly, and getcha some of that!