• Preheat oven to 350°F (177°C). Line an 8x8" pan with parchment, leaving overhang for easy removal.

Make the Shortbread Crust

• In a bowl, whisk together flour, cornstarch, sugar, and salt. Using a pastry cutter, a fork or your hands cut in cold butter until the mixture resembles fine crumbs. Mix in vanilla just until combined.
• Press evenly into the pan. Bake 18–20 minutes, until edges are lightly golden.

Make the Lemon Filling

• In a bowl, combine the sugar and lemon zest and using your fingers rub together until fragrant and pale yellow. (this step releases the oils for extra lemon flavor!)
• Whisk in the flour. Add eggs one at a time, whisking gently until smooth. Do not overly whip, we do not want to incorporate too much air. Stir in the lemon juice and salt.
• Immediately pour the filling over the hot crust, then gently tap the pan on the counter to release any air bubbles.
• Reduce oven to 325°F (163°C) and bake 20–25 minutes, until center is just set (no jiggle).
• Cool completely at room temperature then chill for at least 2 hours in the refrigerator. Do not skip this step, the lemon bars need time to set.
• Using the parchment paper overhang lift the bars out of the pan, slice, and dust generously with powdered sugar. Enjoy!