Preheat your oven to 350°F (175°C) and grease a cake pan. Sift the flour into a bowl to remove lumps and set aside.
In a clean mixing bowl, beat the egg whites with cream of tartar using an electric mixer until soft peaks form. Gradually add half of the sugar, continuing to beat until glossy stiff peaks develop.
In a separate bowl, whisk together the egg yolks, remaining sugar, vanilla extract, and melted butter until smooth and slightly thickened.
Gently fold the egg yolk mixture into the whipped egg whites, using a spatula, until the batter is uniform but airy—be careful to keep as much volume as possible.
Gradually sift the flour over the batter, folding softly after each addition to maintain the light texture.
Pour the batter into the prepared cake pan, smoothing the top with the spatula. Gently tap the pan on the counter to release any large air bubbles.
Bake in the preheated oven until the cake is golden brown and a toothpick inserted into the center comes out clean, about 30 minutes. The cake will feel light but set.
Remove the cake from the oven and let it cool in the pan for 10 minutes before transferring it to a wire rack to cool completely. The top should be slightly cracked and fragrant.
Once cooled, slice the cake gently with a serrated knife to reveal its light, fluffy interior with an even crumb.
Serve slices on a plate, enjoying the delicate texture and subtle vanilla aroma. Perfect for pairing with tea or coffee for a comforting treat.
