Apple Streusel Coffeecake

Preheat oven to 350 °F (175°C). Grease a 9-inch round cake pan. In a small bowl combine flour and baking powder. Beat together eggs, milk and vanilla in another small bowl. Next, combine sugar and butter in a large mixing bowl. Beat with an electric mixer on medium speed until creamy. Alternately add flour mixture and egg mixture, beating well after each addition; end with flour mixture. Spread into prepared cake pan. Arrange apples on top, gently pressing into batter. Bake for 20 minutes. While the cake bakes, make the streusel topping by combining flour, powdered sugar and cinnamon in a small bowl. Cut in remaining 2 tablespoons butter until crumbly. Next, make the glaze by mixing together powdered sugar and enough water to form a smooth consistency that's just thin enough to drizzle; set aside. When cake is ready, sprinkle top with streusel topping. Bake for 15 to 18 more minutes, or until toothpick inserted near center comes out clean. Cool in pan on wire rack. Drizzle with powdered sugar glaze.