1. In large bowl cream butter and 1/3 cup of the sugar until very light and fluffy, about 4 minutes.
2. Add the vanilla exract, then beat to combine.
3. Add the flour and salt, and mix on low speed until the flour is just incorporated.
4. Using a rubber spatula, transfer the dough to a piece of plastic wrap and wrap completely. Refrigerate for an hour, or until the dough is cool to the touch and mostly firm.
5. Position one rack in the center and another in the lower third of the oven, heat to 375ºF.
6. Remove the dough from the fridge and, using your hands , make 18 walnut-sized balls of dough, about 2 tablespoons each. Divide these evenly between the baking sheets, 3 inches apart, and press down on each cookie to form a slightly flattened disk.
7. Sprinkle 1/4 teaspoon of sugar evenly over the top of each cookie.
8. Using oven mitts or pot holders, transfer the baking sheets to the oven and bake until cookies are golden brown around the edges, about 16 to 18 minutes, exchanging positions of baking sheets after 8 minutes.
9. Using oven mitts or pot holders, remove the baking sheets from the oven and set on wire racks to cool completely before removing the cookies from the baking sheets with a metal spatula. Be careful-these cookies are fragile while they're warm.