1/2 cup (1 stick) salted butter, melted
1 teaspoon vanilla
1 cup golden brown sugar
1 cup all-purpose flour
1 teaspoon flaky salt, such as kosher, Maldon sea salt or fleur de sel (or 1/4 teaspoon table salt)
Preheat the oven to 350 degrees and grease an 8×8 metal baking pan.
Melt the butter in a medium saucepan or in a large microwavable bowl and beat in the sugar, egg, vanilla and flour. Turn the mixture into the prepared pan.
From a height of at least 8 inches, sprinkle the salt over the surface of the batter, being sure to get some onto the edges and corners. (Raising your hand high helps distribute the salt more evenly.)
Bake for 15 to 17 minutes, until lightly browned and just set in the center. Gooey is better than dry for these bars. Cool before cutting into 64 pieces.