Salted Vs. Unsalted Butter Unsalted is best. This is used in both the shortbread crust and to make our lemon topping silky smooth and rich.
Preheat oven to 350 F (177C) and line a 9×13 inch glass or ceramic baking pan with parchment paper on the bottom and sides.
Mix ingredients for the crust in a mixer. The dough will be slightly crumbly. Press into the baking pan and prick gently with a fork. Bake for 20 minutes.
Stir eggs, egg yolks, lemon juice, sugar, and salt. Add butter and heat on stovetop over medium heat. Stir until thickened, about 10-12 minutes.
Remove from heat and pour through a mesh strainer to remove any lemon or egg bits.
Pour the curd evenly over the crust (the crust does not need to cool). Return to oven and bake for 20 minutes or until set. The center will be just slightly jiggly.
Allow to cool at room temperature to keep from cracking. Then transfer to the refrigerator for 1-2 hours to cool completely. Dust evenly with powdered sugar and cut into squares.