Bake 9 to 11 minutes or until a wooden toothpick inserted in the center comes out clean. Remove from oven and cool in pan 5 minutes. Remove to a wire rack to cool completely.
To make the lemon frosting:
In a small bowl, beat the 2 tablespoons softened butter and the 1/4 teaspoon lemon zest with an electric mixer at medium speed for 30 seconds. Add powdered sugar and 2 teaspoons of the lemon juice. Beat until combined. Beat in enough of the remaining lemon juice, 1 teaspoon at a time, to make a thick frosting. Using a pastry bag fitted with a star tip, pipe frosting onto each brownie. (Or spoon into a small self-sealing plastic bag. Snip off corner. Pipe frosting onto each brownie.) Chill for 30 minutes.
Note: This is a recipe I saved from Better Homes and Gardens.