01 -
Preheat oven to 325°F. Grease and optionally line a 9×9-inch baking dish with parchment paper.
02 -
Separate eggs into yolks and whites carefully.
03 -
Whisk egg yolks with granulated sugar until pale and fluffy.
04 -
Stir melted butter and lemon zest into the yolk mixture until fully combined.
05 -
Sift flour into the mixture and fold gently until just incorporated.
06 -
Gradually pour in lemon juice followed by lukewarm milk, mixing gently; expect a very thin batter.
07 -
In a separate clean bowl, beat egg whites with salt to stiff peaks.
08 -
Fold whipped egg whites into lemon batter in three portions, being careful to preserve airiness.
09 -
Pour batter into prepared baking dish and smooth surface. Bake for 45 to 55 minutes until the top is golden and center remains slightly jiggly.
10 -
Allow to cool completely at room temperature, then refrigerate for at least 2 hours before slicing.
11 -
Dust the top with powdered sugar and garnish with lemon slices if desired.