TART DOUGH

1. In a large bowl, add the unsalted butter and granulated sugar. Using a hand mixer or a stand mixer fitted with paddle attachment, beat on medium speed until creamy, about 2 minutes. Add in the egg yolk. Beat again until combined. The mixture will now be light and fluffy.
2. In a separate bowl mix together the all purpose flour and salt.
3. Add the dry ingredients to the wet ingredients and mix together until the mixture is crumbly. Using your hands or a mixer fitted with the dough hook attachment, knead the dough until combined. You will have a smooth dough at the end.
4. Cover the dough tightly with a plastic wrap and let it chill in the refrigerator for atleast 30 minutes or overnight.
5. Preheat your oven to 350ºF (177ºC) and grease a 8 or 9 inch tart pan with a nonstick spray. Set aside.
6. Once chilled, allow the dough to rest at room temperature for about 10 minutes. It should be cool yet pliable when touched. Using a tiny bit of flour or between two pieces of parchment paper, roll the dough out using a rolling pin to about ¼ to ⅛ inch thick.
7. Roll the dough out into a ¼ inch thick circle using a rolling pin of diameter around 2-inch larger than the base of your tart pan.
8. Gently lift and press the dough circle into the greased tart pan. Press the dough into the sides and trim the dough hanging out by running the back of a knife around the top edge of the pan. Fill in any gaps or cracks by pressing in bits of dough.
9. Line the dough with a small piece of parchment paper and fill it with pie weights or lentils.
10. Blind bake the tart for about 15 minutes or until it has golden brown edges.
11. Remove the baking tray from the oven and line the browned edges with foil. Remove the pie weights and parchment paper. Return the baking tray to the oven and bake the tart for around 8-10 minutes.
12. Remove the pan from the tray and transfer to a wire rack. Let the shell cool completely before removing it from the pan.

LEMON CURD

1. Place the cubed butter and lemon zest in a large bowl.
2. Place a medium saucepan filled with two inches of water over medium low heat. In a medium bowl that serves as a double boiler, whisk together sugar, eggs and salt until combined. Slowly add the lemon juice and stir to incorporate.
3. Place the bowl over the pot with water and heat the curd over medium low heat, stirring often until the mixture thickens and coats the back of a spoon. Be sure to stir the curd evenly as it cooks, scraping the bottom and sides of the bowl as you go. The curd is done when the mixture is thick and the temperature measures 165ºF using an instant read thermometer.
4. Remove the curd from the heat and pour it through a fine mesh strainer into the bowl with the butter and lemon zest.
5. Whisk to combine well, stirring until all of the butter is melted and the curd is smooth.
6. Pour the curd into the prepare tart crust and bake for an additional 15 minutes. Be sure the oven temperature was lowered to 325ºF. The center should not be liquid but set with a slight jiggle when you wobble the pan. Do not over bake.
7. Remove from oven and cool on cooling rack until room temperature. 
8. Using a hand mixer or a stand mixer fitted with paddle attachment, beat the egg white until foamy. Add in the cream of tartar and slowly the granulated sugar and beat until you get stiff peaks.
9. Transfer meringue to a piping bag fitted with star tip and pipe on top of the lemon tart as desired. 
10. Place tart in the refrigerator for 4 hours or overnight.
11. Slice and serve cold. Dust with confectioner’s sugar if desired.