Preheat oven to 180 degrees C. Grease and flour a 20cm springform pan.
Cake: Sift together the flour, baking powder and salt. Set aside. In a large bowl, cream together the butter and sugar until light and fluffy. Beat in the egg. Beat in the flour mixture alternately with the milk, mixing just until incorporated. Stir in the blueberries. Pour batter into prepared pan.
Crumble Topping: In a small bowl, combine brown sugar, flour, cinnamon and chopped pecans. Cut in butter until crumbly. Sprinkle over the batter.
Bake in the preheated oven for 40 to 45 minutes, or until a toothpick inserted into the centre of the cake comes out clean. Allow to cool.