Blueberry Crumb Coffee Cake

1 1/2 C all-purpose flour
2 tsp baking powder
1/4 tsp salt
1/2 C butter or margarine, softened
1/2 C sugar
1 egg
2 C fresh or frozen (not thawed) blueberries
1/2 C milk
Topping:
1/4 C all-purpose flour
1/4 C sugar
1/2 tsp cinnamon
3 Tbsp butter or margarine

Preheat oven to 375. Mix flour, baking powder and salt on waxed paper. Cream softened butter and sugar in large mixing bowl until light and fluffy. Beat in egg. Place blueberries in bowl; dust with small amount of flour mixture. Toss to coat. Add remaining flour mixture and milk alternately to creamed mixture, mixing continually. Gently fold blueberries into batter. Mix dry topping ingredients in bowl. Cut in butter until crumbly. Spread batter into greased and floured 8" square baking dish. Sprinkle topping over batter. Bake 45 minutes or until topping is golden brown. Cut into squares; serve warm.