Combine flour, baking powder, soda, and salt. Set aside. Cream margarine and granulated sugar with electric mixer. Add eggs one at a time, beating well. Add flour mixture alternately with sour cream and vanilla to batter. Combine brown sugar, nuts, and cinnamon for streusel and set aside ½ cup. Toss the remainder in with the blueberries. Spread one third of batter in a 10-inch greased and floured tube pan. Sprinkle with half of the berry mixture, then spread another third of batter and sprinkle with remaining berry mixture. Top with remaining batter. Sprinkle on ½ cup reserved streusel. Bake at 350 degrees-375 degrees for 60-65 minutes. Cool 10 minutes.
“This recipe is a special favorite with our guests and is requested over and over.” Alternate layers of moist sour-cream cake and chewy fruit streusel. -Cleftstone Manor, Bar Harbor, Maine