Preheat oven to 325°F and set aside a 10-inch tube or angel food pan.
In a large mixing bowl, whip the egg whites with 1/2 cup sugar and cream of tartar until stiff and glossy. Set aside.
In a small bowl, combine Gluten Free 1-to-1 Baking Flour, baking powder, salt, and remaining 1 cup sugar and set aside.
In a clean large bowl, beat yolks, milk, oil, and vanilla extract until thoroughly combined. Add the flour mixture and beat until well blended, about 2 minutes with an electric mixer.
Add a large scoop of the whipped egg whites to the cake batter and mix gently but thoroughly. Add the remaining egg whites and gently fold into the cake batter using a large wire whisk, making sure to scrape down the bottom of the bowl frequently.
Transfer the batter into the tube or angel food pan and bake at 325°F for 50 minutes without opening the oven door during this time. Increase heat to 350°F and bake an additional 10 minutes. The cake is done when the surface springs back immediately after pressing on it with a finger.
Cool the cake upside down for 30 minutes, resting the pan over a bottle-necked jar or on 2 - 4 thick wooden spoon handles, before unmolding. Serve with glaze, powdered sugar, airy frosting, or whipped cream and fruit.
