Cream the softened butter, gradually add the sugar, beating them together until the mixture is light and fluffy. Add the eggs, one at a time, beating well after each egg is added. Stir in the 2 teaspoons of lemon juice. Combine the flour and baking powder and stir into the creamed mixture, mixing well.
Spread the batter evenly into a greased and floured 13"x9"x2" glass baking dish. Sprinkle with the blueberries and remaining lemon juice. Combine the flour, sugar and almonds for the topping. Cut in the butter until the mixture resembles coarse meal. Sprinkle the topping over the berries.