Step #4 Add eggs, one at a time, beating well after each addition.
Step #5 Sift dry ingredients together & slowly add egg mixture, alternating with sour cream & ending with flour mixture (this is the part I'm not understanding).
Step #6 Stir in 1 c blueberries, & add vanilla.
Step #7 Pour 1/2 of the batter in the pan & top this with remaining c of blueberries, sprinkle with brown sugar.
Step #8 Top off with remaining batter & bake for 45-50 mins.