For The Cake For The Frosting To Garnish

1. Warm your oven's temperature to 275°F (135°C).
2. Apply grease and flour to a 9 x 13 pan.
3. In a small bowl, blend the mashed banana with the lemon juice; keep it aside.
4. In a separate medium bowl, stir together flour, baking soda, and salt; keep this aside.
5. In a large bowl, make sure to cream 3/4 cup of the butter with 2 1/8 cups of the sugar until the mixture is light and fluffy.
6. Beat in eggs, one at a time, then stir in 2 tsp of vanilla.
7. Switch between adding the flour mixture and the buttermilk to the butter mixture and beat.
8. Stir in the set-aside banana mixture.
9. Pour the batter you've prepared into the prepared pan and bake it in the preheated oven for an hour or until a toothpick inserted into the center comes out clean.
10. Take the cake out of the oven and immediately place it directly into the freezer for 45 minutes; this will ensure a moist cake.
11. For the frosting, make sure to cream the butter and cream cheese until smooth.
12. Beat in 1 teaspoon of vanilla.
13. Gradually add the icing sugar and beat on low speed until combined, then on high speed until the frosting is smooth.
14. Spread the frosting over the cooled cake.
15. If you wish, sprinkle chopped walnuts over the top of the frosting.