PREHEAT oven to 350 degrees.
COMBINE yolks, 1/4 of the sour cream and vanilla. Set aside. Mix together dry ingredients in large bowl. Add butter and remaining sour cream. Mix well. Gradually add egg mixture in 3 batches, beating well after each addition.
RESERVE 1/3 of batter. Spread remaining into prepared 9-inch springform pan. Sprinkle with 3/4 cup Streusel Filling. Top with apple slices. Drop rest of batter over the fruit. Sprinkle with the Streusel Topping.
BAKE until toothpick inserted in center comes out clean, 55 to 65 minutes. Remove from oven; cool on wire rack.
STREUSEL TOPPING AND FILLING: Place sugars, nuts and cinnamon in bowl; mix well. Reserve 3/4 cup for Filling. Add flour, butter and vanilla to remain sugar mixture, blending well until Topping forms coarse, crumbly texture.