Preheat the oven to 350 degrees and grease three 6" (or two 9") cake pans with cooking spray.
In a medium bowl, mix together flour, salt and baking soda and set aside.
In a large mixing bowl, using an electric mixer with a paddle attachment, cream butter and sugar until light and fluffy (about 3 minutes).
Beat in eggs one at a time and then add vanilla extract.
In a separate small bowl, mash 1 cup of bananas. Once bananas are mashed, add them to the sugar mixture and mix until just combined.
On low speed alternatively add flour mixture and buttermilk until just combined (starting and ending with flour mixture). Do not over mix!
Evenly divide batter between greased pans and bake for 25-30 minutes or until a toothpick comes out of the center of the cake clean.
Let pans cool on top of a cooling rack.