Scalloped Potatoes

I figured I should copy this recipe down since I have such trouble spelling "scalloped". I don't really measure all the ingredients out but I have made it twice because it is such a simple recipe. 
 This recipe was taken from tasteofhome.com and is posted under "Never-Fail Scalloped Potatoes".

Ingredients

• 2 tablespoons butter
• 3 tablespoons all-purpose flour
• 1 teaspoon salt
• 1/4 teaspoon pepper
• 1-1/2 cups fat-free milk
• 1/2 cup shredded reduced-fat cheddar cheese
• 1-3/4 pounds potatoes, peeled and thinly sliced (about 5 medium)
• 1 medium onion, halved and thinly sliced
•  paprika to sprinkle over first layer

Directions

• In a small nonstick skillet, melt butter. Stir in the flour, salt and pepper until smooth; gradually add milk. Bring to a boil. Cook and stir for 2 minutes or until thickened. Remove from the heat; stir in cheese until blended.
• Place half of the potatoes in a 1-1/2-qt. baking dish coated with cooking spray; layer with half of the onion and cheese sauce. Repeat layers.
• Cover and bake at 350° for 50 minutes. Uncover; bake 10-15 minutes longer or until bubbly and potatoes are tender. Yield: 6 servings.