1Preheat oven to 325 degrees.
Grease and flour three 9-inch cake pans.
2Sift together flour and baking soda and set aside.
3Put butter and sugar in a large mixing bowl and cream together until smooth.
Slowly pour in the eggs, mixing well between addition. Stir in the mashed bananas.
4Add dry ingredients and buttermilk alternately, beginning and ending with flour mixture.
Stir in vanilla extract and pecans.
5Divide batter among prepared pans and bake for 25 mins. or until tops are brown. Remove from oven and allow to cool for 5-10 mins, then turn out onto racks to cool completely.
6Frosting & Filling:
7In a small bowl, mix mashed bananas and lemon juice together and set aside.
8In another bowl, with an electric mixer, cream together butter and sugar.
Add mashed bananas, blending well.
Stir in vanilla extract.
9Assembly: Spread a layer of icing on one of the cake rounds, then top with a layer of sliced bananas.
Place the 2nd cake round on top of the bananas and repeat with more icing, then sliced bananas.
Place 3rd layer on top, smooth icing over the sides and top of cake with the remaining frosting.
10Refrigerate overnight. Remove from fridge and leave at room temp. for 3 hours before serving.