I got this recipe from an old friend ..it was his grandmother's recipe and it came from Puerto Rico where she made these cakes every day and sold them to the local market. It is always a HUGE hit when I make it for any occasion. My family loves it, I've made it for work parties and everyone loved it there also! It's actually very easy to make and it's very YUMMY to eat!
Preheat oven to 350 degrees. Grease and flour 9 x 13 baking pan. Separate 6 eggs and make sure to keep yolks because you will use both whites and yolks in this cake. Whip the egg whites in a metal mixing bowl until you get a merengue-like consistency and then add in the sugar very slowly. Then add the egg yolks in one at a time and beat very well after each one. Then stir in the teaspoon of vanilla extract. Slowly add in the cup of flour and stir stir well. You want the batter to maintain a very fluffy appearance. Pour into the pan and bake for 20 minutes. Do not over-bake. Cool on rack in pan. Poke holes in cake with a toothpick once cooled.
Mix together well the sweetened condensed milk, the evaporated milk and the cup of regular milk and pour over the cake and cool in refrigerator overnight. Top with the Cool Whip before serving and if there is any of the milk in the bottom of the pan you can also put this on top of the can when you serve it.