Preheat oven to 350° F. Butter an 8-inch round pan and line with parchment paper. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment, combine flour, sugar, baking powder, and salt. Slowly add butter and mix on low-medium speed until crumbly.
In a measuring glass, whisk together egg whites, milk, and vanilla. Add ½ of wet mixture to mixing bowl at medium speed. Add remaining half of wet mixture and continue to mix until combined.
Transfer batter to prepared pan. Bake for 20-30 minutes until cake is set and golden in color. Insert a toothpick in center of cake to test doneness. Let sit in pan for a couple of minutes before molding. Let cool to room temperature on wire rack. Slice cake into desired thickness.
Place 8 inch cake ring (2-inch high) on serving plate. Line cake ring with an acetate strip (2.5inch high strip). Place cooled cake inside cake ring.