2 1/2 cups unbleached flour
Stir together flour, baking powder and soda. In large bowl beat together butter, 1 1/4 cups sugar, vanilla and lemon peel. Beat in eggs one at a time, beating well after each addition. Beat in sour cream until well blended. At low speed gradually beat in flour mixture until blended. Spoon about one-third of batter into greased and floured 9-inch tube pan. Sprinkle with one-half of the Blueberry Filling (below). Repeat layers. Spread with remaining batter. Sprinkle with Topping (below). Bake on rack below center in a preheated 350° oven until a cake tester inserted in center comes out free of batter.
Cool on a wire rack for 5 minutes. Loosen edges and around tube and turn out on rack to cool completely. Invert on a cake platter.