Preheat your oven to 350°F (175°C) and prepare a 9-inch round baking pan with parchment paper and cooking spray.

Separate the egg yolks from the whites, beat the whites until stiff peaks form (3-5 minutes) and set aside.

In a bowl with yolks, add sugar and beat until pale and fluffy. Mix in melted butter and vanilla extract.

Sift in flour, then add lemon juice and zest, stirring until just combined.

Pour in lukewarm milk, stirring until smooth, but avoid over-mixing.

Gently fold in the egg whites, preserving some volume for texture.

Pour the batter into the prepared pan and bake for 40-60 minutes, checking for doneness.

Let it cool in the pan for about 10 minutes, then turn it out onto a wire rack and cool completely. Dust with powdered sugar before serving.