• Preheat oven to 350°F. No need to preheat if using a convection oven.

Make the Cookie Base

• In a medium-sized mixing bowl add the flour and cut in the butter and crumble together to create a sand-like texture. Add salt and baking powder and combine. Add the vanilla and eggs and press mixture together using your hands. If it seems a tad dry add a sprinkle of water. Option to melt the butter to create a wetter texture and leave out the added sprinkled water.
• Spray an 11 x 8 inch baking dish (11 cup Pyrex) with olive oil. Press the cookie dough into the bottom of the dish.

  For an even cleaner finish, use parchment paper and let it reach a bit over the edges of the dish to make it easier to remove.
• Bake on 350°F for about 15-17 minutes.

  Use middle rack for conventional oven and bottom rack for convection oven.

  Meanwhile, make the lemon filling.

Make the Lemon Filling

• Wash lemons. Zest 2 lemons to equal about 1 ¼ tablespoon zest.
• Juice lemons to equal 1 cup (about 4 lemons).
• In a medium-sized bowl combine zest, lemon juice, eggs, granulated sugar, and flour. Whisk until well combined. If it's still a little lumpy with the flour, use a mixer or immersion blender (I use a tiny milk frother) until smooth.

Put the Bars Together

• When you remove the cookie base from the oven, decrease the oven temp to 325°F.
• Poke at the surface of the crust with a fork (gently to just pierce the surface) to give it some texture. This will help the lemon filling stick more.
• Pour the filling over the cookie base. Bake at 325°F for 25 minutes.
• Increase temperature to 350°F (keeping oven door closed) for a few minutes. If you want a darker top, increase the heat even higher for a few minutes.
• Cool lemon bars on a cooling rack. Once cooled, transfer to the fridge to completely chill.

  If using parchment paper, pull the entire bake out of the dish and set it on a flat surface.

  Cut bars into squares and dust with powdered sugar, or blended granulated sugar.