Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan and line the bottom with parchment paper for easy removal.
In a large mixing bowl, whisk together the milk, granulated sugar, melted butter, lemon zest, lemon juice, vanilla extract, and salt until well combined.
Gradually add the flour to the mixture, whisking until smooth and free of lumps.
In a separate bowl, beat the egg whites with cream of tartar until stiff peaks form.
In another bowl, whisk the egg yolks until pale and slightly thickened. Gently fold the egg yolks into the milk mixture until combined.
Carefully fold the beaten egg whites into the batter, being cautious not to deflate the mixture.
Pour the batter into the prepared cake pan and bake for 40-45 minutes, or until the top is golden brown and a toothpick inserted in the center comes out clean.
Allow the cake to cool in the pan for about 10 minutes, then invert onto a serving plate. Remove the parchment paper and let it cool completely.
Dust with powdered sugar before serving, if desired.