Whisk together flour, salt, sugar, baking powder, and baking soda in a medium bowl. Set aside. Whisk together buttermilk, egg, melted butter and vanilla in a 2-cup measuring cup or small bowl.
Pour the buttermilk mixture into the flour mixture and stir together until just combined. Pour batter into waffle iron and cook to your waffle iron's instructions. Serve with your favorite syrup and toppings.