Preheat oven to 350 degrees F. Line an 8 x 8 pan with foil, lightly spray with cooking spray.
Cut together butter, flour and powdered sugar until mixture resembles coarse meal and press into an even layer into prepared pan. Bake for 15 minutes.
Mix together sugar, flour and baking powder. Add in eggs, lemon juice and lemon rind.
Pour over hot, baked crust and bake for 20-25 minutes or until edges are golden brown and mixture is set.
Mix together powdered sugar and enough lemon juice to make a glaze soft enough to drizzle over lemon bars while they are still warm. Glaze, let cool then cut into squares.
