Quatre-quarts Cake

This is a traditional french cake from Brittany. I just wanted to simple cake without any flavouring or rich icing. The recipe is from http://myfrenchcuisine.blogspot.com . I think I'm going to be trying a lot of these recipes. The cake turned out really authentic...

Take 3 large eggs and weigh them. They should weigh about 2 oz. each (60 grams).
Weigh the same amount of self raising flour: 6 oz. (180 grams) or 1 1/4 cups
Weigh the same amount of sugar: 6 oz. (180 grams) or 3/4 cup
Weigh the same amount of butter: 6 oz. (180 grams) or 3/4 cup (1 1/2 sticks).You can use unsalted and salted butter (50-50), or unsalted butter alone with a good amount of salt (up to 1 teaspoon).

Pour the sugar in a large bowl. Pour the melted butter and blend it in with a wooden spoon until smooth.
Separate the egg yolks from the whites. Set the whites aside.
Add the egg yolks to the sugar-butter mix. Stir well (with the wooden spoon). The more energetically you beat, the fluffier the cake.
Slowly add the sifted flour and incorporate it gradually as it falls on the batter.
Add some salt (up to a whole teaspoon). This isn't needed if you are using salted butter.
Add a pinch of salt to the egg whites and beat until stiff peaks.
Incorporate the egg whites to the batter, one big spoonful at a time, very delicately, making under-and-over motions until evenly blended. The foam (air bubble) shouldn't "break". This is also a very important step in getting a fluffy cake.
Pour the batter in a buttered cake tin - I used a flower shaped silicon mould, which looked really pretty.
Bake at 350F (180C) for about 45 minutes or until baked (if you stick a knife in the center of the cake it should come out dry).