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

Separate the eggs, placing yolks in one bowl and whites in another; let whites sit at room temperature for 15 minutes.

Combine yolks and sugar in a mixing bowl; beat until pale yellow and slightly thickened, about 2-3 minutes.

Add melted butter and vanilla extract to the egg mixture; mix until well combined.

Gradually sift in the flour and mix gently until just combined. Set aside.

Add lemon juice and zest to the batter; stir until well incorporated.

Pour in milk while stirring; ensure a smooth, cohesive batter.

Fold in the room temperature egg whites gently to maintain a light texture.

Pour the batter into the prepared pan and bake for 40-60 minutes or until the top is firm.

Let cool completely in the pan; dust with powdered sugar before slicing.