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.
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.
