In a bowl, combine the first four ingredients; cut in the butter until crumbly. Set aside. In a bowl, cream butter and sugar. Beat in eggs, one at a time. Stir in vanilla. Combine flour, baking powder and salt; add to the creamed mixture alternately with milk. Mix well. Spoon two-thirds of the batter into a greased 9-in. springform pan. Sprinkle with two-thirds of the reserved crumb mixture. Top with blueberries and remaining batter and crumb mixture. Bake at 350° for 65-70 minutes or until a toothpick inserted in the center comes out clean. Cool for 10 minutes before removing sides of pan. Dust with confectioners' sugar.