Preheat oven to 275. Grease and flour a 9x13" pan.
In a small bowl, mix mashed banana with the lemon juice; set aside.
In a medium bowl, mix flour, baking soda and salt; set aside.
In a large bowl, cream 3/4 cup butter and 2 1/8 cups sugar until light and fluffy.
Beat in eggs, one at a time, then stir in 2 tsp. vanilla.
Beat in the flour mixture alternately with the buttermilk.
Stir in banana mixture.
Pour batter into prepared pan and bake in preheated oven for one hour or until toothpick inserted in center comes out clean.
Remove from oven and place directly into the freezer for 45 minutes. This will make the cake very moist.
For the frosting, cream the butter and cream cheese until smooth.
Beat in 1 tsp. vanilla.
Add icing sugar and beat on low speed until combined, then on high speed until frosting is smooth.
Spread on cooled cake.
Sprinkle chopped walnuts over top of the frosting, if desired.
These were the notes for this recipe: This is one of (if not) the BEST banana cake I have ever tasted! I thought the oven temp of 275° sounded a little low, but this cake baked up (and rose) beautifully in my oven at this temp after pretty much exactly one hour. I do not know if the little "freezer trick" to this recipe is what ensured its moistness or not, but I did it, and it was exceptionally moist & delicious. Would be interesting to see if it still came out as great if this step was skipped. All I know is that I followed this recipe EXACTLY as stated (except that I had no buttermilk, so I subbed with a mix of lemon juice & milk) and I got exceptional results. So moist and yummy...a dense cake, similar in texture to a carrot cake... I personally would not call this frosted banana bread :o) Depending on the amount of frosting you like you can decide whether to half the recipe or not. I used the full recipe and had some leftover. I sprinkled on the chopped walnuts and threw this baby in the fridge and cut it the next day...TO DIE FOR! I really liked it slightly chilled, but great at room temp too! It got better each day it sat, I always make this cake at least the day before I need or want it. I was extremely pleased with this cake and will be making it over & over again!! So glad I came across this one!! (on another website). (* * Just to update the recipe, (based on some of the reviews), the baking time may vary based on individual ovens. It was RIGHT ON for my oven, but some others have stated it has taken 1 hour 10 minutes, 1 hour 20 minutes, and my sister just informed me that it took 1 hour 30 minutes in her oven!!!!!)