Preheat the oven to 350℉. Spray a metal 13x9 inch pan with nonstick spray.
In a large bowl, whisk together the flour, sugar, baking powder and salt.
Place the butter in a small saucepan over medium heat. Cook 6 minutes or until lightly browned, stirring often. Pour into a small bowl and let cool. Then add the egg whites to the butter and whisk together (make sure the butter is not hot or it will cook the egg whites!!) Pour the butter mixture into the flour mixture and stir just until everything is all combined. Spread the batter evenly into the prepared pan. Bake 30 minutes, or until a toothpick inserted into the middle comes out clean. Cool, then slice and EAT.