Blueberry Cake with Cinnamon Topping

1/4 cup butter
2/3 cup sugar
1 beaten egg
1/2 cup milk
1 tsp vanilla
2 cups flour
2 tsp. baking powder
1/2 tsp. salt
1 pint blueberries

topping:
1 tsp cinnamon
1/8 stick butter
1/2 cup sugar

Cream butter and sugar together
Beat in egg, stir in milk and vanilla, stir in remaining dry ingredients fold in blueberries

Pour and spread into a  9"x 9"pan
sprinkle on cinnamon topping

bake 350 F. for 50 minutes