Sift flour, salt, baking powder into a bowl, then reserve.
separate eggs from yolks. In a bowl add sugar, yolks beat until yolks are pale yellow then add vanilla extract.
add the flour mixture and milk into the yolks, (do not overbeat), set aside
Beat egg whites on high speed until soft peaks form, then fold in your previous mixture with the whites.
Spray baking oil to a rectangular cake pan, then add your butter to it, bake at 350F - 180C for 30 - 35 min, until the center is cooked, once cooked let it cool,
Once it's completely cooled, make some "holes" with a fork and add the "Milk Syrup" to the cake. (little by little, pour it all around the cake) Refriragete the cake for at least 12 hours