Beat egg whites (at room temperature) until soft peaks form; gradually add sugar and salt, beating until very stiff. Fold in pecans. Spread pecan mixture in prepared pan. Bake at 325° for 30 to 35 minutes or until mixture is browned and all butter is absorbed, stirring at 10 minute intervals to coat evenly. Remove to waxed paper while still warm; cool completely. Store pecans in an airtight container.