Crumb-Topped Blueberry Cake

2 c All-purpose flour

2/3 c Sugar

3 ts Baking powder

1/2 ts Baking soda

1 ts Salt

2 Eggs

1 c Milk

1/2 c Butter or margarine, melted

2 tb Lemon juice

2 c Fresh blueberries *

2/3 c Sugar

1/2 c All-purpose flour

1/2 ts Cinnamon

4 tb Soft butter or margarine

1 c Chopped walnuts

* if using frozen berries, thaw CRUMB TOPPING: In small bowl combine 2/3 cup sugar, 1/2 flour, 1/2 t. cinnamon, 4 T. soft butter or margarine, and 1 cup chopped walnuts. Stir until mixture is evenly blended and crumbly in appearance. Into large mixing bowl measure the flour, sugar, baking powder, baking soda and salt. Stir well to blend. Into large measuring cup, combine eggs, milk, butter and lemon juice. Stir luquid ingredients into dry ingredients until blended. Turn into buttered 13-by-9-inch baking dish. Sprinkle blueberries evenly over the batter. Sprinkle with the Crumb Topping. Bake at 375 degrees for 40 to 45 minutes. Serve warm.