Preheat the oven to 350 degrees F (175 degrees C).
Sift all-purpose flour and baking powder into a bowl. Stir in potato starch.
Beat 3/4 cup plus 2 tablespoons butter in a bowl using an electric mixer until light and fluffy. Add confectioners' sugar and vanilla sugar; beat until just combined. Add egg yolks and sour cream; mix well. Whisk lemon zest, lemon juice, and almond extract into the batter.
Beat egg whites in a glass, metal, or ceramic bowl using clean beaters until stiff peaks form.
Beat flour mixture into the batter until no dry spots remain. Gently fold in raisins and egg whites until evenly incorporated.
Liberally grease a 6-cup Bundt(R) cake pan (approximately 8 inches in diameter) with 1 1/2 tablespoons butter. Sprinkle evenly with bread crumbs. Spoon batter into the prepared pan.
Bake in the preheated oven until a toothpick inserted into the center of the cake comes out clean, 30 to 40 minutes. Cool slightly before inverting cake onto a serving plate.
