Preheat the oven to 350 degrees F (175 degrees C). Lightly grease a 9x13 baking dish with cooking spray.

In a medium bowl, add flour and baking powder (and cinnamon, if desired) and mix to combine.

In a medium mixing bowl, beat ¾ cup sugar and egg yolks until light in color and doubled in size (about 3 minutes).

Stir in dry ingredients, milk and vanilla and mix until just combined.

In a glass bowl, beat egg whites (make sure no yolk is in there) on high speed until soft peaks form (about 5 minutes). Gradually, add ¼ cup remaining sugar, continuing to beat on high speed until medium peaks form (about 3 minutes).

Slowly, add the egg whites into the yolk mixture, carefully stirring with a spatula until the batter is just combined and there are no more yellow or white streaks.

Pour the batter in to the prepared pan and bake for 30 - 35 minutes or until a toothpick inserted into the middle comes out clean. Let cake cool completely (it will deflate a bit).

One cake is cooled, make your milk mixture by mixing together the sweetened condensed milk, evaporated milk and heavy cream in a medium bowl.

Poke cake all over with a fork and slowly pour the milk mixture over the entire cake making sure to get inside the fork holes. Refrigerate for at least 4 hours.

Once ready to serve, whip the heavy cream, powdered sugar, and vanilla together until stiff peaks form in a cold, large metal bowl (we like to use our Kitchen-Aid). Spread over the cake. Sprinkle with cinnamon and serve.