Preheat your oven to 350°F (175°C).
In a mixing bowl, whisk together the sugar, flour, and salt.
In another bowl, beat the egg yolks and add the milk, lemon juice, and lemon zest. Mix well.
Combine the wet and dry ingredients, mixing until smooth.
In a separate bowl, beat the egg whites until stiff peaks form. Gently fold the egg whites into the batter.
Pour the batter into a greased baking dish. Place the dish in a larger pan filled with hot water, about halfway up the sides of the baking dish.
Bake for 45 minutes, or until the top is golden and the cake is set.
Let it cool slightly before serving. Enjoy!