Preheat oven to 350 degrees.
Lightly coat an 8 by 8-inch baking pan with vegetable spray. Cut a length of parchment paper to fit the pan allowing the paper to come up to the top on two opposite sides. Trim the excess above the edge of the pan. Cut another sheet to fix in the opposite direction also trimming at the top of the pan. Set aside.
Whisk together the flour, baking powder and salt together in a small mixing bowl. Set aside.
In a medium medium bowl combine the butter and granulated sugar; beat until light and fluffy. Add the eggs one at a time mixing well after each additional until incorporated. Blend in the vanilla and mix another 30 seconds, scraping the sides and bottom of the bowl with a spatula. Add the lemon juice zest and blend just until combined. Using the rubber spatula, fold in the dry ingredients until blended. Do not over-mix.
Spread the batter evenly in the prepared pan and bake for 22-24 minutes. The edges will just start to brown and a toothpick inserted into the center should come out clean. Remove from the oven and cool completely in the pan.
Lift the cooled Blondies out of the pan using the parchment paper and transfer to a cutting board. Whisk together the glaze ingredients until smooth. Pour over the Blondies and spread until the top is covered. Slice and serve.