Preheat the oven to 350 degrees. Spray a 9 by 13 inch baking dish with nonstick baking spray. Set aside.
In the bowl of an electric mixer, cream butter and sugar together on medium speed. Add eggs one at a time, and mix until incorporated.
Add vanilla bean paste, lemon juice, and lemon zest and mix.
Add salt and flour and mix on low speed until just incorporated. Do not over mix.
Pour the batter evenly into the pan, and bake for 28-30 minutes at 350 degrees, or until a toothpick inserted into the center comes out clean.
Allow to cool for 15 minutes, and then pour glaze over the top and spread it evenly to the edges. Cool completely and then cut into bars. A plastic knife works very well! Store in an airtight container.
For the Glaze
Add powdered sugar, lemon juice, lemon zest, vanilla bean paste, and heavy cream into a bowl and whisk together with a fork. Add water as needed to thin the glaze. It should be pourable. Pour and spread the glaze over the slightly cooled bars.