Preheat oven to 375°F. Spray an 8½ x 4½-inch loaf pan with nonstick cooking spray. Set aside.

To the bowl of a stand mixer with a paddle attachment, add the sugar, butter, sour cream, egg, lemon juice, and lemon zest. Beat until creamy. (You could also use a handheld mixer.)

In a separate bowl, whisk together flour, baking powder, and salt.

With the mixer on low, alternate between adding the flour mixture and the milk, beginning and ending with the flour mixture.

Gently fold in about 1 ¾ cups of blackberries, reserving ¼ cup for the topping.

Pour the batter into the prepared loaf pan and top with the reserved blackberries.

To make the crumble topping, mix together the flour, granulated sugar, brown sugar, salt, and melted butter in a small bowl.

Top the batter with the crumble.

Bake the loaf for 65 minutes. The bread is done when an inserted toothpick comes out with a few crumbs, but no wet batter. Let the loaf cool before adding the glaze.

In a medium bowl, whisk together the confectioners' sugar and water. Add more water until the glaze reaches your desired consistency.

Drizzle the glaze over the cooled loaf. Slice and serve.