Preheat your oven to 350°F (175°C) and grease an 8-inch round baking pan, lining the bottom with parchment paper.

In a large mixing bowl, whisk together the egg yolks and sugar until pale yellow and fluffy, about 3–5 minutes.

Gradually blend in the melted butter and vanilla extract until creamy and smooth.

Sift the all-purpose flour into the egg mixture, gently folding it in until just combined. Stir in the lemon juice and zest.

Slowly pour in the milk, stirring continuously until the mixture is smooth and free of lumps.

Beat the egg whites until stiff peaks form, then gently fold them into the batter.

Pour the batter into the prepared baking pan, smoothing the top. Bake for 40–60 minutes, checking at 35 minutes.

After baking, allow the cake to cool in the pan for 15 minutes before transferring it to a wire rack to cool completely.