Heat up your waffle iron according to its particular instructions.
While the waffle iron is heating, add the melted butter, egg, milk, and vanilla extract in a medium-sized bowl. Whisk to combine.
Add in the all-purpose flour, white sugar, baking powder, and salt. Whisk until smooth.
Spray down the waffle iron, or brush on some butter with a pastry brush.
Pour in half of the mixture (about 1/3 cup) into the waffle iron. Close and cook to the iron's instructions—usually until it beeps.
Repeat for the second waffle.
Serve with berries, syrup, butter, or any other toppings you desire.