1-Heat oven to 325ºF: Heat oven to 325ºF. If your butter is not very soft, melt two tablespoons of it. Place the remainder in a large bowl. Pour the melted butter into the bowl; then stir with a wooden spoon to combine or until the butter is the texture of mayonnaise. Add the salt and stir to combine. Add the sugar and vanilla if using; then stir again to combine. Finally, add the flour and stir just until the flour is absorbed – the dough will still be lumpy.
2-Press dough into an ungreased (or parchment: Press dough into an ungreased (or parchment paper-lined for easy removal) 8- or 9-inch-square baking pan. Bake until golden brown, 35 to 40 minutes for 9-inch pan, 45 to 50 minutes for 8-inch. Transfer to a wire rack to cool. Cut into squares, bars or wedges while still warm. Sprinkle with a tablespoon or two of sparkling, superfine, or granulated sugar, if using.