Preheat the oven to 350°. Spray a 10-inch springform pan with vegetable oil cooking spray. In a medium bowl, whisk the flour, baking powder, baking soda and salt. In a large bowl, using a handheld electric mixer, beat the butter until creamy. Add the granulated sugar and beat at medium speed until light and fluffy. Then beat in the eggs and vanilla. Add the sour cream and bananas; beat at low speed just until blended. Add the dry ingredients and beat until smooth. Scrape the batter into the prepared pan and smooth the top.