For the cake

1. Preheat oven to 275°. Grease and flour two 9″ round pans.
2. In a small bowl, mix mashed banana with the lemon juice; set aside.
3. In a medium bowl, mix flour, baking soda and salt; set aside.
4. In a large bowl, cream butter and sugar until light and fluffy.
5. Beat in eggs, one at a time, then stir in the vanilla extract.
6. Beat in the flour mixture alternately with the buttermilk, beginning and ending with the flour mixture.
7. Fold in banana mixture until just incorporated. Be careful not to overmix.
8. Pour batter evenly into prepared pans and bake in preheated oven for one hour or until toothpick inserted in center comes out clean.
9. Remove from oven and place directly into the freezer for 45 minutes*. This will make the cake very moist.

For the frosting

1. In an electric mixer, mix cream cheese and butter until smooth and creamy. Add in cocoa powder and mix until there are no lumps and the color is completely combined.
2. One cup at a time, mix in the powdered sugar until completely smooth. Use immediately, or keep in the refrigerator tightly wrapped for up to 24 hours.

For the cake assembly

1. Remove cake layers from the freezer. Place one cake layer on a cake or serving plate. Spread about 1/2 cup of frosting onto the cake in an even layer with an offset spatula. If using, lay out the banana slices so that they cover the surface of the cake. Place second cake layer on top.
2. Frost the entire cake with a thin layer of icing (a crumb coat) using an offset spatula. Put into the refrigerator for 1/2 hour, and then frost as desired with the remaining frosting.