Preheat oven to 350 degrees F. Spray a 9 x 13 inch baking dish with non stick baking spray liberally.
In the bowl of an electric mixer fitted with the paddle attachment, or a large bowl and a hand mixer, cream the butter and sugar until light and fluffy, about 3-5 minutes.
Add the eggs one at a time and mix well to combine. Add the vanilla extract and mix.
In a medium bowl, whisk the flour, baking powder, and salt to combine. Add the mixture to the mixer in ½ cup batches and mix just until incorporated. Scrape well to ensure the batter is well combined.
Pour into prepared baking dish and spread in an even layer. It will double in size while baking.
Bake for 25-35 minutes or until a toothpick comes out clean. Allow cake to cool in the pan for 30-45 minutes or until completely cooled.
In a 4-cup measuring cup or medium sized bowl, pour in condensed milk, evaporated milk, and heavy cream, whisk well to combine.
When cake is completely cool, poke the cake several times with a fork across the surface. You want it well poked across the entire cake. Slowly drizzle all of the milk mixture over the cake as evenly as possible, focusing on the edges of the cake.
Allow cake to absorb the milk mixture for 30 minutes. In a large, clean bowl, whip heavy cream with sugar and vanilla extract until thick and spreadable, then smooth over the surface of the cake.
Decorate cake with whole maraschino cherries or an even sprinkling of ground cinnamon or fresh berries. Let refrigerate for 4 hours to overnight, or cut into squares and serve immediately if you can't wait.