Preheat oven to 350°F (175°C) and grease an 8x8 inch square baking pan.
In a medium bowl, whisk together 1.5 cups flour, baking powder, and salt.
In a large bowl, cream together 1/2 cup softened butter and 3/4 cup granulated sugar until light and fluffy.
Beat in the egg and vanilla extract until well combined.
Gradually add the dry ingredients to the wet ingredients, alternating with the milk, mixing until just combined.
Gently fold in the fresh berries by hand.
Spread the batter evenly into the prepared baking pan.
In a separate small bowl, combine the topping flour, brown sugar, 1/4 cup granulated sugar, and cinnamon.
Cut in the cold cubed butter using a pastry cutter or fork until coarse crumbs form.
Sprinkle the crumb topping evenly over the cake batter.
Bake for 45 to 50 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool in the pan on a wire rack for at least 15 minutes before slicing.