Ingredients (12 servings)

• 6 eggs
• the weight of the eggs in sugar 
• half of the weight of the eggs in flour
• 1 teaspoon of baking powder
• zest of an orange
• milk (optional)
• butter and flour for the baking pan

Instructions (Time: 1 hour)

Preheat your oven to 180ºC (350ºF). Butter and flour the baking pan. Separate the egg whites and the egg yolks, and beat the egg yolks with the sugar until you get a creamy and pale mixture.

Add the zest of an orange to the batter and mix well.

On a separate bowl, beat the egg whites until they’re stiff.

Add the flour and the baking powder to the egg yolk and sugar mixture and mix well. If you feel that the batter it’s too dry and you can’t mix the flour in properly, add milk one tablespoon at a time. The moisture of the batter will depend on the size of your eggs. It should not be runny - the batter should stand on it’s own.

Fold in the egg whites, bringing the mixture from the bottom of the bowl to the top.

You’ll get a fluffy and bubbly batter.

Transfer the batter to a baking pan.

And cover the baking pan with aluminum foil. Bake in the oven for a total of 30 minutes. After 15 minutes remove the aluminum foil so that the cake can get some color.

To check if the cake is done pierce the cake with a toothpick. The toothpick should come out clean.

Remove the cake from the baking pan and let it cool down.