Ideally, start the recipe by weighing eggs and adapting the weight of each ingredient, which must be the same as the weight of the eggs. Use a food scale for accurate ingredient measurements.

Weigh 5 large eggs with shells. Use an egg separator to separate the egg whites from the yolks. Weigh the empty eggshells and subtract their weight from the egg weight. You will then have the weight of the eggs without shells.

While letting the egg whites and egg yolks get to room temperature, weigh each of the other three ingredients of the same weight as the egg weight.

Preheat the oven to 355°F (180°C). Grease and flour an 8-inch (20 cm) nonstick bread pan or line it with parchment paper. If using a silicone loaf pan, there is no need to grease.

Cut butter into equal pieces and place in a small saucepan. Melt it over low-medium heat, transfer it to a clean bowl, and let it cool for 10 minutes.

Place egg yolks with sugar in the bowl of a stand mixer or a large mixing bowl. Beat the yolk mixture until it whitens.

Gradually add flour with baking powder (if used) and cooled melted butter to the egg mixture while mixing at low speed.

In a separate bowl, whisk egg whites at medium-high speed until stiff peaks. Gently add 1/2 of the beaten egg whites into the main preparation and mix with a rubber spatula. Add the rest of the egg whites and mix.

Pour the batter into the prepared pan. Dip the handle of a wooden spoon in cold water and incise 2 cm through the entire length of the cake. This will prevent it from denting while baking.

Bring the cake to the middle of the oven and immediately decrease the oven temperature to 320°F (160°C). Bake for 65-70 minutes until golden brown. Check for doneness with the blade of a knife after 50 minutes: if it comes out clean, the cake is done.

Remove the cake from the oven and let it cool in the pan for 10 minutes. Unmold it, and cool it completely on a cooling rack.