Preheat your oven to 275°F. Grease and flour three 8-inch round cake pans. Set them aside.

In a small bowl, combine the mashed bananas with the lemon juice. Set aside. In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.

In a large bowl, beat the butter and sugar together until light and fluffy. Add the eggs one at a time, beating well after each addition. Mix in the vanilla, sour cream, and applesauce. Alternately add the flour mixture and the milk, starting and ending with the flour. Fold in the banana mixture.

Divide the batter evenly among the prepared pans (about 2 1/2 cups per pan). Bake for 40 to 50 minutes, or until a toothpick inserted in the center comes out clean.

Immediately after removing the pans from the oven, place them in the freezer. Be careful to set them on a heat-safe surface. Let the cakes cool completely before frosting, about 30 to 40 minutes in the freezer. (Alternatively, cool at room temperature, but the freezer stops the cooking process faster and keeps the cake extra moist.)

For the frosting: In a large bowl, beat the butter and cream cheese until smooth. Gradually beat in the powdered sugar, cinnamon, vanilla, and salt. Start on low speed until combined, then increase to high and beat until smooth and fluffy.

Assemble the cake by placing one layer on a serving plate. Spread a thick layer of frosting on top. Repeat with the second and third layers. Frost the top and sides of the cake as desired. Sprinkle a little cinnamon around the outside for garnish. Store in the refrigerator until ready to serve.