Preheat oven to 350 degrees F (175 degrees C). Grease and flour an 8 inch square pan.
Step 2
In a large glass or metal mixing bowl, beat egg whites until stiff peaks form. Fold 1/3 of the whites into the batter, then quickly fold in remaining whites until no streaks remain. Pour batter into prepared pan.
Step 3
In a large bowl, combine sugar, salt and melted butter. Beat in the flour. Stir in the lemon zest and lemon juice. Combine milk and egg yolks, and add to lemon mixture.
Step 4
Set cake pan in a water bath. Bake in the preheated oven for 40 minutes, or until top is lightly browned. Serve warm or cold.
