Preheat oven to 350°.
Coat a 9-inch round springform pan with cooking spray, and dust the pan with 2 teaspoons flour.
Place butter in a large microwave-safe bowl. Cover and microwave at high 1 minute or until butter melts. Add granulated sugar, stirring with a whisk. Add eggs; stir well. Stir in buttermilk and next 6 ingredients (buttermilk through baking soda); stir well. Lightly spoon 1 1/2 cups flour into dry measuring cups; level with a knife. Add flour, stirring just until blended (do not overstir). Stir in blueberries and pecans. Spoon mixture into prepared pan, spreading evenly.
Bake at 350° for 45 minutes or until lightly browned and a wooden pick inserted in center comes out clean. Cool 10 minutes in pan on a wire rack. Sprinkle with powdered sugar. Cut into wedges.