Lighter Airy Pound Cake

Via Smitten Kitchen - adapted by Isabelle

200g (1 cup) butter, at room temperature
200 grams (1 1/2 cups) all-purpose flour
2,5 ml (1/2 teaspoon)baking powder
1 ml (1/4 tsp.) salt
4 eggs separated
186 grams (3/4 cup) sugar
15 ml (1 1/2 tablespoons) Cognac
7,5 ml ( 1 1/2 teaspoons) grated lemon zest

Preheat the oven to 350 degrees.
Butter and flour a loaf pan.
Sift the flour onto waxed paper and then spoon it gently back into the sifter, adding the baking powder and a good pinch of salt. Sift the mixture twice more, each time spooning it lightly into the sifter.
Using an electric mixer, whip the egg whites until they hold soft peaks and then gradually beat in 100 grams (1/2 cup) of the sugar, 30 g (2tablespoons) at a time.
Transfer to a bowl.
Cream the butter until light and fluffy.
Beat in the remaining 86 grams (six tablespoons) of sugar until fluffy.
Beat in the egg yolks until light and lemon-colored and then add the Cognac and zest.
Gradually fold the sifted flour mixture into the butter-egg mixture.
Fold in the beaten egg whites just until the batter is smooth.
Pour batter into the prepared pan and bake in the oven for 35 to 45 minutes or until a toothpick pierced in the center comes up clean.
Cool in pan ten minutes on a rack, then cool the rest of the way out of the pan.

Blueberry sauce:
500 ml (2 cups) fresh or frozen blueberries
125 ml (1/2 cup) sugar
45 ml (3 tablespoons) cornstarch 
30 ml (2 tablespoons) lemon juice
pinch salt
10 ml (2 teaspoons) pure vanilla

Wash blueberries and drain.
In a saucepan, combine sugar, cornstarch and salt.
Add blueberries and stir well.
Heat over medium heat and stir in lemon juice.
Bring to a boil, stirring constantly.
Once it boils reduce heat and cook 5 minutes.
Add vanilla and pour into a bowl or serving dish.
Put plastic wrap over the surface to avoid forming a skin.

Bon Appétit!