Coat a 9 x 13 cake pan with nonstick spray. You can also use parchment paper for the bottom of the pan to prevent sticking.
In a medium bowl, combine milk and lemon juice. Stir and set aside.
In a large bowl, beat the butter and both sugars on medium speed for 2 minutes. Add in eggs, vanilla, salt, baking soda and mix until smooth.
Add in the flour and milk mixture in alternating additions on low speed, beginning and ending with flour.
Mix in the bananas until just incorporated. Don't over beat.
Pour mixture into the pan and bake for 55 minutes. Start checking your cake befoe the timer goes off. You may have to add a few more minutes to start seeing the top turn golden brown. Check the cake by inserting a toothpick in the middle and if it comes out clean, your cake is done.
Let the cake cool completely before adding on the frosting.
Frosting
In a large bowl mix together the butter and cream cheese for about 2 minutes until creamy. Turn the mixer to low and add the powdered sugar. Add lemon juice and lemon zest if desired.
Add the vanilla and 1 tablespoon of milk. Turn mixer to medium speed and mix until the mixture is combined well. If the icing is too thick, add more of the milk.
Pour over cooled cake and spread evenly.
Notes
NOTE: I store this cake in the fridge and serve it at room temperature.