Take the milk out of the refrigerator and heat it until lukewarm. Add the butter to the warmed milk and let it melt inside for enough time to dissolve.
In a bowl, combine the baking powder, flour, salt, and sugar. You can also add ground cinnamon to the listed ingredients. Mix all the ingredients well.
Separate the egg whites and yolks. Beat the egg whites until stiff peaks form.
Mix the egg yolks with the melted butter and the milk mixture along with the vanilla extract. Pour the mixture into the bowl from step 2 and mix well to avoid lumps. Gently fold in the beaten egg whites.
Preheat the waffle iron and lightly grease it with melted butter. You can apply the butter using a brush. Pour the prepared batter into the hot waffle iron, ensuring the batter fills slightly below the edge of the iron. The waffle is done when it turns golden brown.
The baked waffle can be served with honey, fruit or jam.