Preheat the oven to 375 degrees F. Grease a 9 by 5 inch loaf pan. In a small mixing bowl, combine 1/4 cup of the sugar, brown sugar, 1/3 cup flour, 4 tablespoons butter, and 1/2 teaspoon cinnamon. Mix until the topping is incorporated. Using an electric mixer, cream the remaining sugar and butter together. Add the egg, 1/2 and 1/2, sour cream , and lemon juice, blend until smooth. In a mixing bowl, sift the remaining flour, baking powder, salt and remaining cinnamon together. With the machine running, slowly add the flour until all the flour is incorporated. Fold in the blueberries and lemon zest. Pour the batter into the prepared pan. Sprinkle the topping on top of the batter. Bake the bread for about 50 minutes, or until the top is golden brown. Remove the pan from the oven and cool for 5 minutes. Remove the bread from the oven and cool on a wire rack. Slice and serve./