Heat oven to 350°F. Coat 13 x 9 x 2-inch baking pan with cooking spray.
In bowl, combine flour and sugar. With pastry blender, cut in butter until mixture resembles fine crumbs. Stir in pecans. Set aside.
In large bowl, mix flour, cinnamon, salt, and baking soda. In large bowl, beat together on medium speed, sugar, mashed banana, oil, eggs, buttermilk, and vanilla until blended, 1 to 2 minutes. On low speed, gradually add flour mixture until blended. Stir in pecans. Pour into prepared pan. Crumble Crunch Topping evenly over top.
Bake at 350°F for 50 to 55 minutes, until wooden pick tests clean. Let cake cool in pan on rack. To serve, sprinkle with sugar, if desired. Refrigerate, covered, up to 3 days.