Preheat oven to 350°F. Grease and flour 2 round 9-inch cake pans.
In a bowl, mix flour, Splenda, cocoa, baking powder, baking soda, and salt.
In a stand mixer, blend buttermilk, oil, eggs, and vanilla. Slowly add dry ingredients until combined. Mix in coffee.
Pour batter into pans and bake for about 25 minutes, or until a toothpick comes out clean.
Cool cakes on a rack. Meanwhile, make frosting: whip cream cheese until smooth. In another bowl, mix milk and sugar-free pudding mix until smooth. Add pudding to cream cheese gradually, then fold in whipped topping.
To assemble, place one cake layer on a plate, spread frosting over it, add the second layer, and frost the top and sides. Refrigerate until serving