Best Ever Banana Cake with Cream Cheese Frosting

Preheat the oven to 275 degrees.Brush the 9 x 13 cm pan with butter and sprinkle with flour.In a small bowl, combine the banana puree and lemon juice; set aside.In a medium bowl, combine the flour, baking soda, and salt; set aside. .In a large bowl, whisk together 3/4 cup butter and 2 1/8 cups sugar until light and fluffy.Beat the eggs one at a time, then add 2 teaspoons of vanilla.Whisk flour mixture alternately with buttermilk.Add the banana mixture.Pour the batter onto the prepared pan and bake in the preheated oven for an hour or until a toothpick inserted in the middle comes out clean.Remove from the oven and place directly in the freezer for 45 minutes. This will make the cake very moist.For the frosting, whisk together the butter and cream cheese until smooth.Whisk with 1 teaspoon vanilla.Add the powdered sugar and beat on low speed until smooth, then on high speed until the frosting is smooth.Spread on the cooled cake. 15 If desired, sprinkle the icing with chopped walnuts.