Preheat the oven to 320°F (160°C) and prepare a 9-inch round cake pan by lining it with parchment paper and spraying with cooking spray.

Separate the eggs, placing egg whites in one bowl and yolks in another.

Whip the egg whites until stiff peaks form, about 3-4 minutes.

In the yolk bowl, whisk together the egg yolks and sugar until creamy and pale yellow, about 2-3 minutes.

Melt the butter, let it cool, then add to the yolk mixture along with vanilla extract, mixing until combined.

Gradually add flour, lemon juice, and lemon zest to the yolk mixture, mixing gently until combined.

Slowly mix in the lukewarm milk until fully integrated into the batter.

Gently fold the whipped egg whites into the batter until small lumps remain.

Pour the batter into the prepared pan and bake for 40-60 minutes until slightly jiggly in the center.

Cool the cake completely in the pan on a wire rack, then dust with powdered sugar before serving.