In a large bowl, mix together flour, salt, baking powder and sugar; set aside. Preheat waffle iron to desired temperature.
In a separate bowl, beat the eggs. Stir in the milk, butter and vanilla. Pour the milk mixture into the flour mixture; beat until blended.
Ladle the batter into a preheated waffle iron and spread with a heat resistant spatula. Cook the waffles until golden and crisp. Serve immediately.