Preheat oven to 325. Grease and lightly flour two 8-inch round cake pans. (To prepare the cake pans, spray them with cooking spray and the sprinkle some flour. Pat the baking pan while holding it on an angle to spread the flour all over the bottom and some up the sides. Turn the baking pan upside-down, over the sink, and pat on the bottom to get rid of the excess flour.)

Beat butter for a minute, on medium-high speed. Add sugar and beat for a couple of minutes.

Add eggs, one at a time, beating well after each addition. Lower speed to low.

Sift flour, baking soda and salt together.

Add half the flour mixture to the mixer, beat on low until just incorporated. Add half of the buttermilk and mix until just incorporated. Add remaining flour and then remaining buttermilk.

Add vanilla and lemon juice, mix until just combined.

Add mashed banana and mix until just incorporated through the batter.

Divide batter among the two prepared baking pans.

Bake for 33-36 minutes, do a toothpick test to make sure that the toothpick inserted in the center comes out clean.

Let cakes cool for about 10 minutes, then run a butter knife along the sides of the pans and invert the cakes onto a cooling rack to cool completely. Make sure the cakes are completely cooled before frosting.

For frosting: Beat cream cheese on medium-high speed, until smooth, 1-2 minutes. Lower the speed to low and beat in powder sugar and caramel. Scrape sides and bottom of the pan. Turn up the speed back to medium-high and beat for about 3-4 minutes, until the frosting is light, smooth and fluffy. Turn speed back down to low and fold in whipped topping. Scrape sides and bottom of the bowl and fold until all mixed.

To assemble the cake, spread about half the frosting on top of the bottom layer of the cake. Spread half of chopped walnuts all over the top, evenly, in one layer. Drizzle half the caramel all over the nuts.

Top off with the second cake layer and repeat frosting, nuts and caramel layers on top.

(Store in the refrigerator.)