In a large mixing bowl, combine the flour, sugar, baking powder, and salt, whisking well.
In a medium mixing bowl, combine the milk, butter, eggs, and vanilla extract. Whisk until combined. The butter might solidify here, but it's OK.
Pour the wet mixture into the dry ingredients and whisk until JUST combined.
Begin preheating your waffle maker.
When the waffle maker is ready, spray the inside with cooking spray to prevent sticking. Scoop an appropriate amount of batter inside (be careful not to add too much, otherwise it will overflow as it expands). Cook until golden brown. Repeat with the remaining batter.
Nutrition information is calculated using an ingredient database and should be considered an estimate.