Step 1 Heat the oven to 350 degrees. Spray a 12-by-9-inch baking pan with nonstick spray. Mix the flour and powdered sugar in a food processor to blend. Add the butter and pulse until the mixture resembles a coarse meal. Sprinkle the mixture over the prepared baking pan and press the dough evenly over the bottom of the pan. Bake until the crust is golden, about 20 minutes. Transfer the pan to a rack, and cool completely.