The Ultimate Lemon Butter Bar

Name: The Ultimate Lemon Butter Bar
Ingredients: 10 tbsp unsalted butter (cold) (5 ounces = 142 grams),for shortbread; 2 tbsp Powdered sugar (0.5 ounce = 14 grams),for shortbread; 2 tbsp Granulated Sugar(0.75 ounce = 25 grams),for shortbread; 1 1/4 cup All Purpose Flour,bleached (dip and sweep method) (6.25 ounces = 180 grams),for shortbread; 4 x large egg yolks (2 full fluid ounces = 2.5 ounces = 74 grams), for lemon curd; 3/4 cup Sugar(5.25 ounces = 150 grams),for lemon curd; 3 fl oz Lemon Juice, freshly squeezed (about 2 1/2 large lemons) (3.25 ounces = 94 grams)(use a liquid measuring cup),for lemon curd; 4 tbsp unsalted butter, softened (2 ounces = 57 grams),for lemon curd; pinch of salt,for lemon curd; 2 tsp Lemon zest(finely grated) (4 grams),for lemon curd; 2 tbsp Powdered sugar for dusting(0.5 ounce = 14 grams),for lemon curd