Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch pan.
In a large bowl, cream together the butter and sugar until light and fluffy. Add the egg yolks one at a time, beating well with each addition, then stir in the vanilla. Sift together the flour and baking powder. Add the flour mixture alternately with the milk; beat well after each addition. In a large glass or metal mixing bowl, beat egg whites and cream of tartar until whites form stiff peaks. Gently fold the egg whites into the cake batter using a rubber spatula. Spread the mixture evenly into the prepared pan.
Bake in the preheated oven for 25 to 30 minutes, or until a toothpick inserted into the cake comes out clean. Allow to cool.
In a small bowl, stir together the 2 cups heavy cream, evaporated milk and sweetened condensed milk. Pour the mixture over the cake until it wont absorb any more. You may have 1/3 to 1/4 left over. That's okay.
Combine the whipped cream and sugar, spread over soaked cake. Refrigerate cake until serving, Pour leftover milk mixture onto plates and swirl in jam if desired, before setting cake on the plates.