Streusel Küchen

Ingredients

• 1 cup all purpose flour 
• 1.5 teaspoons double-acting baking powder 
• 1.5 cups cake flour 
• 0.3 cup cornstarch 
• 3 large eggs plus 1 egg yolk 
• 0.7 cup brown sugar packed ()
• 0.5 teaspoon ground cinnamon 
• 0.1 teaspoon ground cloves 
• 1 tablespoon lemon zest finely grated
• 2 cups powdered sugar 
• 2 medium size golden delicious apples cored peeled halved cut into 1/8-inch-thick slices
• 0.3 teaspoon salt 
• 1 cup butter unsalted room temperature ()
• 1  vanilla pod split
• 0.3 cup walnuts chopped

Equipment

• bowl
• frying pan
• oven
• hand mixer
• aluminum foil
• springform pan

Directions

1. Mix first 4 ingredients in medium bowl.
2. Add melted butter and stir with fork until moist clumps form. DO AHEAD Can be made 1 day ahead. Cover and chill.
3. Position rack in center of oven and preheat to 325°F. Butter and flour 10-inch-diameter springform pan. Toss apple slices, cinnamon, and cloves in medium bowl. Sift flour, cornstarch, baking powder, and salt into another bowl.
4. Combine butter, powdered sugar, and lemon peel in large bowl; scrape in seeds from vanilla bean.
5. Using electric mixer, beat butter mixture until well blended.
6. Add eggs 1 at a time, beating until well blended after each addition; beat in egg yolk.
7. Add flour mixture and beat just until blended.
8. Spread batter evenly in prepared pan (cake layer will be thin). Slightly overlap apple slices atop batter in concentric circles.
9. Sprinkle streusel evenly over apples (streusel will cover apples).
10. Bake cake until streusel topping is crisp and tester inserted into center of cake comes out clean, about 1 hour 20 minutes. Cool cake in pan on rack 15 minutes.
11. Remove pan sides; cool to lukewarm.
12. Serve lukewarm or at room temperature. DO AHEAD Can be made 1 day ahead. Cool completely. Wrap cake in foil and store at room temperature.