Preheat the oven to 375 degrees
In a large bowl, cream the butter and sugar
Mix the egg into the cream mixture
In a small bowl, sift the flour, salt, and baking powder
To the cream mixture, alternate adding some of the flour mixture and the milk until it is all mixed in
Fold in the berries
Spoon the batter into a greased 9x9 inch baking pan
Use a fork to mix the crumb streusel topping
Sprinkle the crumb topping over the batter
Bake for 40-45 minutes