Grease a 9x9 inch pan. You can also add a piece of parchment paper to the bottom, cut to fit in the square. Preheat the oven to 350 F.
Cream the softened butter (1/2 cup) for about 60 seconds. Add the brown sugar (3/4 cup) and cream together for roughly 3 minutes. Then, add the flour (1 1/2 cups), salt (1/4 teaspoon), and baking powder (2 teaspoons) in thirds, mixing each addition completely before adding the next. The mixture will be very dry.
Beat in the eggs (2). Then beat in the milk (1/2 cup), sour cream (1/4 cup), and vanilla (1 teaspoon) until fully incorporated. Fold in the blueberries (1 1/2 cups). Add the batter to the prepared pan.
Mix together the streusel topping (1/2 cup brown sugar, 1/4 cup flour, 1/4 cup butter, 1 teaspoon cinnamon, 1/2 teaspoon cloves) and sprinkle over the top of the batter. Bake in the oven for 55 minutes, or until a toothpick inserted in the middle comes out mostly clean with a few moist crumbs.
Let stand for 20 minutes before serving. Run a knife along the edges of the cake to help release it from the sides before slicing and serving.