Preheat oven to 350 degrees F. Grease and lightly flour one 9x13 inch cake pan.
In a medium bowl, sift the flour and baking powder together. Set aside.
In a large mixing bowl, cream together the butter and 3/4 cups sugar until fluffy. Add the eggs and the 1/2 teaspoon vanilla extract until well blended.
Add the flour to the butter mixture 2 tablespoons at a time. Mix until well blended. Pour into the prepared cake pan.
Bake at 350 degrees F for 25-30 minutes. Allow to cool for about 30 minutes. Poke holes in the cake with a fork or skewer.
Whisk together the 3 milks: whole, condensed, and evaporated until well blended. Pour over the top of the cake. Allow the liquid to seep into the cake.
In a large bowl using an electric mixer, whip together the whipping cream, the remaining 1/2 cup sugar, and the remaining 1 teaspoon vanilla extract until thick and stiff peaks form. Once the milk liquid has been completely absorbed by the cake, spread the topping over the top of the cake. Dust top with cinnamon, if desired.