Cream butter and sugar, add egg yolks and mashed bananas. In separate bowl, pour boiling water over pecans and set aside. Add lemon juice to banana mixture. Sift flour and baking powder together and add to batter alternately with butter milk and soda mixture. Add pecans.
Beat egg whites with salt until stiff peaks form. Fold in egg whites.
Bake in two 9 inch layer cake pans at 300 for 35, until golden brown and done in center. Remove from oven and cool completely before spreading with fill/frosting.
Filling/Frosting-Mix butter and sugar until creamy. Add bananas, nuts and juice( may need additional confectioners sugar if you like thicker frosting). Spread between layers and on sides and top of cake.