Heat oven to 350 F.
Cream butter and sugar; beat in eggs, bananas, buttermilk and vanilla.
Stir in remaining ingredients just until well combined.
Spread batter into two round cake pans. Bake until deep golden brown (about 30-35 minutes).
Remove from pans; allow to cool completely on wire rack before frosting.
In a small mixing bowl, combine butter, cream cheese, powdered sugar and vanilla. Beat until creamy. Frost one cake completely; top with the second cake and cover with the remainder of the frosting.