Grease with baking spray a bund cake baking form, set aside.
In a large bowl, add the egg whites and whisk until foamy, then add little by little the sugar, mix until getting stiff picks.
In another bowl, mix the flour, together with the cornstarch and the baking powder.
Add the vanilla to the egg mixture, followed by the flour mixture, folded gently.
Stir in the melted butter, again gently fold it into the batter.
Bake on a previously pre-heated oven at 180°C for 30 minutes or until when pricked with a toothpick it comes out clean.
Let the cake for five minutes in the form before turning it out to cool completely.